Add an explicit warning in the Differential transaction log when users skip review

Summary:
Ref T10233. See PHI231. When users ignore the arc land prompt about bad revision states, make it explicitly clear in the transaction log that they broke the rules.

You can currently figure this out by noticing that there's no "This revision is accepted and ready to land." message, but it's unrealistic to expect non-expert users to look for the absence of a message to indicate something, and this state change is often relevant.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T10233

Differential Revision: https://secure.phabricator.com/D18808