R1:a635da68d41e

Provide bucketing for commits in Audit

Summary:
Fixes T9430. Fixes T9362. Fixes T9544. This changes the default view of Audit to work like Differential, where commits you need to audit or respond to are shown in buckets.

This is a bit messy and probably needs some followups. This stuff has changed from a compatibility viewpoint:

- The query works differently now (but in a better, modern way), so existing saved queries will need to be updated.
- I've removed the counters from the home page instead of…