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.
# setup: from decimal import Decimal ; A = [Decimal('2.1') for i in range(1000)] ; B = [Decimal('3.2') for i in range(1000)]  # noqa
# run: large_decimal_list(A, B)


def large_decimal_list(A, B):
    return [a * b for a, b in zip(A, B)]

# setup: from decimal import Decimal ; A = [Decimal('2.1') for i in range(1000)] ; B = [Decimal('3.2') for i in range(1000)]  # noqa
# run: large_decimal_list(A, B)


def large_decimal_list(A, B):
    return [a * b for a, b in zip(A, B)]
