Backport simplified %py_provides
    
    This is a smallest possible backport of https://src.fedoraproject.org/rpms/python-rpm-macros/pull-request/52
    
    Notable simplifications:
    
    - there is no Lua library
    - %python_provide remains untouched and the logic is not shared with %py_provides
    - there are no pythonXY-foo provides on Fedora < 33