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: atomicwrites
  version: 1.4.0
source:
  sha256: ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a
  url: https://files.pythonhosted.org/packages/55/8d/74a75635f2c3c914ab5b3850112fd4b0c8039975ecb320e4449aa363ba54/atomicwrites-1.4.0.tar.gz
test:
  imports:
  - atomicwrites

package:
  name: atomicwrites
  version: 1.4.0
source:
  sha256: ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a
  url: https://files.pythonhosted.org/packages/55/8d/74a75635f2c3c914ab5b3850112fd4b0c8039975ecb320e4449aa363ba54/atomicwrites-1.4.0.tar.gz
test:
  imports:
  - atomicwrites
