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.
#ifndef DOCSTRING_H
#define DOCSTRING_H

int
set_method_docstring(PyMethodDef* method, PyObject* parent);

int
add_methods_and_set_docstrings(PyObject* module,
                               PyMethodDef* methods,
                               PyObject* docstring_source);

int
docstring_init();

#endif /* DOCSTRING_H */

#ifndef DOCSTRING_H
#define DOCSTRING_H

int
set_method_docstring(PyMethodDef* method, PyObject* parent);

int
add_methods_and_set_docstrings(PyObject* module,
                               PyMethodDef* methods,
                               PyObject* docstring_source);

int
docstring_init();

#endif /* DOCSTRING_H */
