This change upgrades Sphinx for RBTools to the latest 7.x release and

bumps the sphinx-tabs extension to the latest version as well. There are

several things that appeared as warnings that I've fixed up:

We were listing rbtools.commands twice in the coderef index.
The source_suffix setting was changed long ago from a simple string

  to a dictionary. The older version we were on silently dealt with it,

  but 7.x warns.
We were triggering a warning about circular references from some

  changes in autosummary. I've added the recommended workaround,

  suppressing those warnings.
configuration/tfs.rst had an underline that wasn't the length of the

  header.
Added a few __autodoc_excludes__ lines to prevent warnings about

  conflicting references.
The SquashedDiff and DiffHistory namedtuples were triggering some

  weird warnings about duplicate fields in the generated docs. Switching

  to typed NamedTuple classes fixes these.
The inline-link syntax used in docstrings in the SOS code was wrong.
Several doc comments in config/config.py were using :rbt-command:

  instead of :rbtcommand:

Built the RBTools manual and verified that everything worked well.