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: pyparsing
  version: 2.4.7
source:
  sha256: c203ec8783bf771a155b207279b9bccb8dea02d8f0c9e5f8ead507bc3246ecc1
  url: https://files.pythonhosted.org/packages/c1/47/dfc9c342c9842bbe0036c7f763d2d6686bcf5eb1808ba3e170afdb282210/pyparsing-2.4.7.tar.gz
test:
  imports:
  - pyparsing

package:
  name: pyparsing
  version: 2.4.7
source:
  sha256: c203ec8783bf771a155b207279b9bccb8dea02d8f0c9e5f8ead507bc3246ecc1
  url: https://files.pythonhosted.org/packages/c1/47/dfc9c342c9842bbe0036c7f763d2d6686bcf5eb1808ba3e170afdb282210/pyparsing-2.4.7.tar.gz
test:
  imports:
  - pyparsing
