[3.11] gh-135374: Adjust test for setuptools' replacement of distutils (GH-138796)

[3.11] gh-135374: Adjust test for setuptools' replacement of distutils (GH-138796)

ensurepip installs a bundled copy of distutils, which overrides
the stdlib module. This affects several tests. This commit:

- skips distutils in test___all__, as we're unlikely to break
  `__all__` in a security-fix-only branch (and if we do it's not
  much of a a big deal)
- skips importability tests of distutils submodules if the
  setuptools hack is detected

Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Emma Smith <emma@emmatyping.dev>