Remove most of the deprecated code scheduled to be removed for 5.0
Review Request #12428 — Created June 30, 2022 and submitted
This change removes the majority of the deprecated code and
functionality that's been scheduled for 5.0. The only one left is
get_orig_commit_id(), which is still used by the Mercurial diff
parsers. That will be a more invasive change, and will be done
Ran unit tests.