bindings/python-cffi: clean up _notmuch_config.py _notmuch_config.py is generated by configure, and cannot be cleaned up by the current python build system, since it is imported as a module by that same build system. Use DISTCLEAN rather than CLEAN for consistency with other configure related things.
python: adjust legacy bindings to py 3.12 Py 3.12 finally pulled the plug on the `SafeConfigParser` class which has been deprecated since py 3.2. We use it in the legacy bindings only, so take the easy route of importing `ConfigParser` as `SafeConfigParser` and monkey-patching so that the class has the expected interface.