Drop setup.py based Python build (#2135561, #2149762)
    
    The setup.py build was only really added for dealing with parallel
    installable Python 2 and 3 builds, and has been quite a PITA otherwise
    because it's not what the upstream builds and tests use. Now that
    the 2to3 transition is thankfully over, we can go back to building the
    extension by ourselves. Only, in the meanwhile people have come to
    depend on the egg-info data so create that from automake, that format is
    not exactly rocket science.
    
    This fixes us accidentally shipping two slightly different Python
    modules for years (#2135719) and building with Python >= 3.12 where
    distutils has been dropped, and does so in upstream compatible manner
    (where a similar approach was taken when transitioning to cmake based
    build system)