Add more compatability shims to SetuptoolsVersion

* Enables indexing the SetuptoolsVersion objects, triggering the
  legacy behavior warning.
* Enables comparing the SetuptoolsVersion object to a tuple, again
  triggering the legacy behavior warning.
Update changelog
Added tag 8.0.2 for changeset 1c03d512e39d
Bumped to 8.0.3 in preparation for next release.
Merge with 8.0.2