Python 3.12 has released, so update the test infrastructure to test
against this version. Update the configure script to look for it when an
explicit Python interpreter isn't chosen.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-id: 20231006195243.3131140-5-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>