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.
from pyodide_build.testing import run_in_pyodide


@run_in_pyodide(packages=["sympy"])
def test_sympy():
    import sympy

    a, b = sympy.symbols("a,b")
    c = sympy.sqrt(a ** 2 + b ** 2)

    c.subs({a: 3, b: 4}) == 5

from pyodide_build.testing import run_in_pyodide


@run_in_pyodide(packages=["sympy"])
def test_sympy():
    import sympy

    a, b = sympy.symbols("a,b")
    c = sympy.sqrt(a ** 2 + b ** 2)

    c.subs({a: 3, b: 4}) == 5
