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: html5lib
  version: '1.1'
requirements:
  run:
  - webencodings
  - six
source:
  sha256: b2e5b40261e20f354d198eae92afc10d750afb487ed5e50f9c4eaf07c184146f
  url: https://files.pythonhosted.org/packages/ac/b6/b55c3f49042f1df3dcd422b7f224f939892ee94f22abcf503a9b7339eaf2/html5lib-1.1.tar.gz
test:
  imports:
  - html5lib

package:
  name: html5lib
  version: '1.1'
requirements:
  run:
  - webencodings
  - six
source:
  sha256: b2e5b40261e20f354d198eae92afc10d750afb487ed5e50f9c4eaf07c184146f
  url: https://files.pythonhosted.org/packages/ac/b6/b55c3f49042f1df3dcd422b7f224f939892ee94f22abcf503a9b7339eaf2/html5lib-1.1.tar.gz
test:
  imports:
  - html5lib
