* m4/python.m4: Add python3.12 and 3.11 as valid interpreters, remove EOL 3.4, 3.5, 3.7 (keep 3.6 because some distributions still ship and maintain it)
* lang/python/Makefile.am: switch from distutils to PEP517 build
* lang/python/setup.py.in: switch from distutils to setuptools, add classifiers up to 3.12, remove 3.4, 3.5, 3.7
* lang/python/doc/src/gpgme-python-howto.org: replace distutils with setuptools
* lang/python/examples/howto/advanced/cython/setup.py: replace distutils with setuptools
* .gitignore: ignore dist-info