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: sympy
  version: '1.8'
requirements:
  run:
  - mpmath
source:
  sha256: 1ca588a9f6ce6a323c5592f9635159c2093572826668a1022c75c75bdf0297cb
  url: https://files.pythonhosted.org/packages/88/b1/e4e620f45949a4cc7c935a0c711f6aac24e875810b68c37148c7402d838f/sympy-1.8.tar.gz
test:
  imports:
  - sympy

package:
  name: sympy
  version: '1.8'
requirements:
  run:
  - distutils
  - mpmath
source:
  sha256: 1ca588a9f6ce6a323c5592f9635159c2093572826668a1022c75c75bdf0297cb
  url: https://files.pythonhosted.org/packages/88/b1/e4e620f45949a4cc7c935a0c711f6aac24e875810b68c37148c7402d838f/sympy-1.8.tar.gz
test:
  imports:
  - sympy
