Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
Unvendor distutils. Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
package:
  name: msgpack
  version: 1.0.2
source:
  sha256: fae04496f5bc150eefad4e9571d1a76c55d021325dcd484ce45065ebbdd00984
  url: https://files.pythonhosted.org/packages/59/04/87fc6708659c2ed3b0b6d4954f270b6e931def707b227c4554f99bd5401e/msgpack-1.0.2.tar.gz
test:
  imports:
  - msgpack
package:
  name: msgpack
  version: 1.0.2
source:
  sha256: fae04496f5bc150eefad4e9571d1a76c55d021325dcd484ce45065ebbdd00984
  url: https://files.pythonhosted.org/packages/59/04/87fc6708659c2ed3b0b6d4954f270b6e931def707b227c4554f99bd5401e/msgpack-1.0.2.tar.gz
test:
  imports:
  - msgpack