libnetwork: clean up vestigial datastore-related code
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**- What I did**
I cleaned up code related to datastores and their configuration across libnetwork, pruning dead code and refactoring what remained. Highlights:
  - Refactored package `drvregistry` to no longer be an ad-hoc Dependency Injection container for network and IPAM drivers, and created separate types for network driver registries and IPAM driver registries
    - The `PluginGetter` dependency is now injected directly into the remote drivers
    - Removed the vestiges of datastore dependency injection
  - Removed `DatastoreConfig` from `discoverapi` as dynamic datastore discovery is unreachable
  - Threw out much of the dead persistence code from package `ipam`

**- How I did it**
Prove that code is unreachable. Delete the dead code. Repeat.

**- How to verify it**
CI.

**- Description for the changelog**
N/A

**- A picture of a cute animal (not mandatory but encouraged)**

![Cat.](https://user-images.githubusercontent.com/274527/214968924-169b4eb9-53a8-4a27-b364-883e1f9168e5.jpg)

libnetwork/ipams/remote/remote.go
package remote

import (
	"fmt"
	"net"

	"github.com/docker/docker/libnetwork/discoverapi"
	"github.com/docker/docker/libnetwork/ipamapi"
	"github.com/docker/docker/libnetwork/ipams/remote/api"
	"github.com/docker/docker/libnetwork/types"
	"github.com/docker/docker/pkg/plugingetter"
	"github.com/docker/docker/pkg/plugins"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

type allocator struct {
	endpoint *plugins.Client
	name     string
}

// PluginResponse is the interface for the plugin request responses
type PluginResponse interface {
	IsSuccess() bool
	GetError() string
}

func newAllocator(name string, client *plugins.Client) ipamapi.Ipam {
	a := &allocator{name: name, endpoint: client}
	return a
}

// Init registers a remote ipam when its plugin is activated
func Init(cb ipamapi.Callback, l, g interface{}) error {

	newPluginHandler := func(name string, client *plugins.Client) {
		a := newAllocator(name, client)
		if cps, err := a.(*allocator).getCapabilities(); err == nil {
			if err := cb.RegisterIpamDriverWithCapabilities(name, a, cps); err != nil {
				logrus.Errorf("error registering remote ipam driver %s due to %v", name, err)
			}
		} else {
			logrus.Infof("remote ipam driver %s does not support capabilities", name)
			logrus.Debug(err)
			if err := cb.RegisterIpamDriver(name, a); err != nil {
				logrus.Errorf("error registering remote ipam driver %s due to %v", name, err)
			}
		}
	}

	// Unit test code is unaware of a true PluginStore. So we fall back to v1 plugins.
	handleFunc := plugins.Handle
	if pg := cb.GetPluginGetter(); pg != nil {
		handleFunc = pg.Handle
		activePlugins := pg.GetAllManagedPluginsByCap(ipamapi.PluginEndpointType)
		for _, ap := range activePlugins {
			client, err := getPluginClient(ap)
			if err != nil {
				return err
			}
			newPluginHandler(ap.Name(), client)
		}
	}
	handleFunc(ipamapi.PluginEndpointType, newPluginHandler)
	return nil
}

func getPluginClient(p plugingetter.CompatPlugin) (*plugins.Client, error) {
	if v1, ok := p.(plugingetter.PluginWithV1Client); ok {
		return v1.Client(), nil
	}

	pa, ok := p.(plugingetter.PluginAddr)
	if !ok {
		return nil, errors.Errorf("unknown plugin type %T", p)
	}

	if pa.Protocol() != plugins.ProtocolSchemeHTTPV1 {
		return nil, errors.Errorf("unsupported plugin protocol %s", pa.Protocol())
	}

	addr := pa.Addr()
	client, err := plugins.NewClientWithTimeout(addr.Network()+"://"+addr.String(), nil, pa.Timeout())
	if err != nil {
		return nil, errors.Wrap(err, "error creating plugin client")
	}
	return client, nil
}

func (a *allocator) call(methodName string, arg interface{}, retVal PluginResponse) error {
	method := ipamapi.PluginEndpointType + "." + methodName
	err := a.endpoint.Call(method, arg, retVal)
	if err != nil {
		return err
	}
	if !retVal.IsSuccess() {
		return fmt.Errorf("remote: %s", retVal.GetError())
	}
	return nil
}

func (a *allocator) getCapabilities() (*ipamapi.Capability, error) {
	var res api.GetCapabilityResponse
	if err := a.call("GetCapabilities", nil, &res); err != nil {
		return nil, err
	}
	return res.ToCapability(), nil
}

// GetDefaultAddressSpaces returns the local and global default address spaces
func (a *allocator) GetDefaultAddressSpaces() (string, string, error) {
	res := &api.GetAddressSpacesResponse{}
	if err := a.call("GetDefaultAddressSpaces", nil, res); err != nil {
		return "", "", err
	}
	return res.LocalDefaultAddressSpace, res.GlobalDefaultAddressSpace, nil
}

// RequestPool requests an address pool in the specified address space
func (a *allocator) RequestPool(addressSpace, pool, subPool string, options map[string]string, v6 bool) (string, *net.IPNet, map[string]string, error) {
	req := &api.RequestPoolRequest{AddressSpace: addressSpace, Pool: pool, SubPool: subPool, Options: options, V6: v6}
	res := &api.RequestPoolResponse{}
	if err := a.call("RequestPool", req, res); err != nil {
		return "", nil, nil, err
	}
	retPool, err := types.ParseCIDR(res.Pool)
	return res.PoolID, retPool, res.Data, err
}

// ReleasePool removes an address pool from the specified address space
func (a *allocator) ReleasePool(poolID string) error {
	req := &api.ReleasePoolRequest{PoolID: poolID}
	res := &api.ReleasePoolResponse{}
	return a.call("ReleasePool", req, res)
}

// RequestAddress requests an address from the address pool
func (a *allocator) RequestAddress(poolID string, address net.IP, options map[string]string) (*net.IPNet, map[string]string, error) {
	var (
		prefAddress string
		retAddress  *net.IPNet
		err         error
	)
	if address != nil {
		prefAddress = address.String()
	}
	req := &api.RequestAddressRequest{PoolID: poolID, Address: prefAddress, Options: options}
	res := &api.RequestAddressResponse{}
	if err := a.call("RequestAddress", req, res); err != nil {
		return nil, nil, err
	}
	if res.Address != "" {
		retAddress, err = types.ParseCIDR(res.Address)
	} else {
		return nil, nil, ipamapi.ErrNoIPReturned
	}
	return retAddress, res.Data, err
}

// ReleaseAddress releases the address from the specified address pool
func (a *allocator) ReleaseAddress(poolID string, address net.IP) error {
	var relAddress string
	if address != nil {
		relAddress = address.String()
	}
	req := &api.ReleaseAddressRequest{PoolID: poolID, Address: relAddress}
	res := &api.ReleaseAddressResponse{}
	return a.call("ReleaseAddress", req, res)
}

// DiscoverNew is a notification for a new discovery event, such as a new global datastore
func (a *allocator) DiscoverNew(dType discoverapi.DiscoveryType, data interface{}) error {
	return nil
}

// DiscoverDelete is a notification for a discovery delete event, such as a node leaving a cluster
func (a *allocator) DiscoverDelete(dType discoverapi.DiscoveryType, data interface{}) error {
	return nil
}

func (a *allocator) IsBuiltIn() bool {
	return false
}

package remote

import (
	"fmt"
	"net"

	"github.com/docker/docker/libnetwork/discoverapi"
	"github.com/docker/docker/libnetwork/ipamapi"
	"github.com/docker/docker/libnetwork/ipams/remote/api"
	"github.com/docker/docker/libnetwork/types"
	"github.com/docker/docker/pkg/plugingetter"
	"github.com/docker/docker/pkg/plugins"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

type allocator struct {
	endpoint *plugins.Client
	name     string
}

// PluginResponse is the interface for the plugin request responses
type PluginResponse interface {
	IsSuccess() bool
	GetError() string
}

func newAllocator(name string, client *plugins.Client) ipamapi.Ipam {
	a := &allocator{name: name, endpoint: client}
	return a
}

// Init registers a remote ipam when its plugin is activated.
//
// Deprecated: use [Register].
func Init(cb ipamapi.Callback, l, g interface{}) error {
	return Register(cb, cb.GetPluginGetter())
}

// Register registers a remote ipam when its plugin is activated.
func Register(cb ipamapi.Registerer, pg plugingetter.PluginGetter) error {
	newPluginHandler := func(name string, client *plugins.Client) {
		a := newAllocator(name, client)
		if cps, err := a.(*allocator).getCapabilities(); err == nil {
			if err := cb.RegisterIpamDriverWithCapabilities(name, a, cps); err != nil {
				logrus.Errorf("error registering remote ipam driver %s due to %v", name, err)
			}
		} else {
			logrus.Infof("remote ipam driver %s does not support capabilities", name)
			logrus.Debug(err)
			if err := cb.RegisterIpamDriver(name, a); err != nil {
				logrus.Errorf("error registering remote ipam driver %s due to %v", name, err)
			}
		}
	}

	// Unit test code is unaware of a true PluginStore. So we fall back to v1 plugins.
	handleFunc := plugins.Handle
	if pg != nil {
		handleFunc = pg.Handle
		activePlugins := pg.GetAllManagedPluginsByCap(ipamapi.PluginEndpointType)
		for _, ap := range activePlugins {
			client, err := getPluginClient(ap)
			if err != nil {
				return err
			}
			newPluginHandler(ap.Name(), client)
		}
	}
	handleFunc(ipamapi.PluginEndpointType, newPluginHandler)
	return nil
}

func getPluginClient(p plugingetter.CompatPlugin) (*plugins.Client, error) {
	if v1, ok := p.(plugingetter.PluginWithV1Client); ok {
		return v1.Client(), nil
	}

	pa, ok := p.(plugingetter.PluginAddr)
	if !ok {
		return nil, errors.Errorf("unknown plugin type %T", p)
	}

	if pa.Protocol() != plugins.ProtocolSchemeHTTPV1 {
		return nil, errors.Errorf("unsupported plugin protocol %s", pa.Protocol())
	}

	addr := pa.Addr()
	client, err := plugins.NewClientWithTimeout(addr.Network()+"://"+addr.String(), nil, pa.Timeout())
	if err != nil {
		return nil, errors.Wrap(err, "error creating plugin client")
	}
	return client, nil
}

func (a *allocator) call(methodName string, arg interface{}, retVal PluginResponse) error {
	method := ipamapi.PluginEndpointType + "." + methodName
	err := a.endpoint.Call(method, arg, retVal)
	if err != nil {
		return err
	}
	if !retVal.IsSuccess() {
		return fmt.Errorf("remote: %s", retVal.GetError())
	}
	return nil
}

func (a *allocator) getCapabilities() (*ipamapi.Capability, error) {
	var res api.GetCapabilityResponse
	if err := a.call("GetCapabilities", nil, &res); err != nil {
		return nil, err
	}
	return res.ToCapability(), nil
}

// GetDefaultAddressSpaces returns the local and global default address spaces
func (a *allocator) GetDefaultAddressSpaces() (string, string, error) {
	res := &api.GetAddressSpacesResponse{}
	if err := a.call("GetDefaultAddressSpaces", nil, res); err != nil {
		return "", "", err
	}
	return res.LocalDefaultAddressSpace, res.GlobalDefaultAddressSpace, nil
}

// RequestPool requests an address pool in the specified address space
func (a *allocator) RequestPool(addressSpace, pool, subPool string, options map[string]string, v6 bool) (string, *net.IPNet, map[string]string, error) {
	req := &api.RequestPoolRequest{AddressSpace: addressSpace, Pool: pool, SubPool: subPool, Options: options, V6: v6}
	res := &api.RequestPoolResponse{}
	if err := a.call("RequestPool", req, res); err != nil {
		return "", nil, nil, err
	}
	retPool, err := types.ParseCIDR(res.Pool)
	return res.PoolID, retPool, res.Data, err
}

// ReleasePool removes an address pool from the specified address space
func (a *allocator) ReleasePool(poolID string) error {
	req := &api.ReleasePoolRequest{PoolID: poolID}
	res := &api.ReleasePoolResponse{}
	return a.call("ReleasePool", req, res)
}

// RequestAddress requests an address from the address pool
func (a *allocator) RequestAddress(poolID string, address net.IP, options map[string]string) (*net.IPNet, map[string]string, error) {
	var (
		prefAddress string
		retAddress  *net.IPNet
		err         error
	)
	if address != nil {
		prefAddress = address.String()
	}
	req := &api.RequestAddressRequest{PoolID: poolID, Address: prefAddress, Options: options}
	res := &api.RequestAddressResponse{}
	if err := a.call("RequestAddress", req, res); err != nil {
		return nil, nil, err
	}
	if res.Address != "" {
		retAddress, err = types.ParseCIDR(res.Address)
	} else {
		return nil, nil, ipamapi.ErrNoIPReturned
	}
	return retAddress, res.Data, err
}

// ReleaseAddress releases the address from the specified address pool
func (a *allocator) ReleaseAddress(poolID string, address net.IP) error {
	var relAddress string
	if address != nil {
		relAddress = address.String()
	}
	req := &api.ReleaseAddressRequest{PoolID: poolID, Address: relAddress}
	res := &api.ReleaseAddressResponse{}
	return a.call("ReleaseAddress", req, res)
}

// DiscoverNew is a notification for a new discovery event, such as a new global datastore
func (a *allocator) DiscoverNew(dType discoverapi.DiscoveryType, data interface{}) error {
	return nil
}

// DiscoverDelete is a notification for a discovery delete event, such as a node leaving a cluster
func (a *allocator) DiscoverDelete(dType discoverapi.DiscoveryType, data interface{}) error {
	return nil
}

func (a *allocator) IsBuiltIn() bool {
	return false
}

:eyes: