Allow Herald to detect when "arc land" would (or did) warn users about failed or ongoing builds. This respects the "Warn on Landing" build plan behavior.
To accomplish this:
- When we close a revision, set a "wrong build state" flag if it lands in the wrong build state.
- If the revision is closed when we hit Herald, look for the flag.
- If not (common for push rules, can happen for commit rules if we race against the revision update worker), hit Harbormaster ourselves and check the current state.