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: Pygments
  version: 2.8.1
source:
  sha256: 2656e1a6edcdabf4275f9a3640db59fd5de107d88e8663c5d4e9a0fa62f77f94
  url: https://files.pythonhosted.org/packages/15/9d/bc9047ca1eee944cc245f3649feea6eecde3f38011ee9b8a6a64fb7088cd/Pygments-2.8.1.tar.gz
test:
  imports:
  - pygments

package:
  name: Pygments
  version: 2.8.1
source:
  sha256: 2656e1a6edcdabf4275f9a3640db59fd5de107d88e8663c5d4e9a0fa62f77f94
  url: https://files.pythonhosted.org/packages/15/9d/bc9047ca1eee944cc245f3649feea6eecde3f38011ee9b8a6a64fb7088cd/Pygments-2.8.1.tar.gz
test:
  imports:
  - pygments
