textproc/py-mkdocstrings: Update to 0.22.0

• Introduce CRYSTAL, PYTHON and PYTHONLEGACY options to reflect the optional dependencies as noted in "pyproject.toml". Leave the last two as non-default for now, because both are mutually exclusive due conflicting dependencies.

• Switch to PEP517 build framework and get rid of the no longer required workarounds for distutils.

• Remove the backported patch for Jinja2 3.1+ compatibility which is also no longer needed.

• Convert the test suite to USE_PYTHON=pytest as well.

Changelogs since 0.17.0:

https://github.com/mkdocstrings/mkdocstrings/blob/0.22.0/CHANGELOG.md