Remove remaining ArcanistDifferentialRevisionStatus references in revision state logic

Summary: Ref T2543. This cleans up all the "when no one is rejecting/blocking and someone accepted, mark the revision overall as accepted" logic to use more modern status stuff instead of ArcanistDifferentialRevisionStatus.

Test Plan:

• Updated revisions, saw them go to "Needs Review".
• Accepted, requested changes to revisions.
• Updated one with changes requested, saw it go to "needs review" again.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18413