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: docutils
  version: '0.17'
source:
  sha256: e2ffeea817964356ba4470efba7c2f42b6b0de0b04e66378507e3e2504bbff4c
  url: https://files.pythonhosted.org/packages/8e/5a/85e35f8692abd8dcd00a67e79c1e45caa6019b8d49d3bee5b2482583d81d/docutils-0.17.tar.gz
test:
  imports:
  - docutils

package:
  name: docutils
  version: '0.17'
source:
  sha256: e2ffeea817964356ba4470efba7c2f42b6b0de0b04e66378507e3e2504bbff4c
  url: https://files.pythonhosted.org/packages/8e/5a/85e35f8692abd8dcd00a67e79c1e45caa6019b8d49d3bee5b2482583d81d/docutils-0.17.tar.gz
test:
  imports:
  - docutils
