Restore some minor state behaviors to Differential on EditEngine

Summary:
Ref T11114. This restores:

• Commandeering should exeucte Herald.
• Commandeering should swap reviewers.
• "Request Review" on an "Accepted" revision should downgrade reviewers so they have to accept again.

Test Plan:

• Commandeered, saw Herald run and reviewers swap.
• Requested review of an accepted revision, saw it drop down to "Needs Review" with "Accepted Prior" on the reviewer.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11114

Differential Revision: https://secure.phabricator.com/D17118