* 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 (clean-local): Remove dist and gpg.egg-info
created by Python 3.9+ on make install.
* lang/python/setup.py.in: switch from distutils to setuptools where
possible, remove obsolete and deprecated -py3 option of swig, 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