Use new Python macros and other related cleanup
    
    - Use pyproject macros
    - Remove %{srcname} macro that makes that specfile harder to read.
    - Fix sphinx build so it can find the `ara` binary
    - Rename python3-ara-server to python3-ara+server to take advantage of
      the automatic dependency generating. Add proper Obsoletes and Provides
      to maintain backwards compatibility.
    - Don't duplicate docs and licenses. Since ara and python3-ara+server
      depend on python3-ara, there's no need to duplicate them.
    - Allow the new macros to handle shebang mangling.