R1:9c24798e64c9

Update Owners auditing rules for multiple reviewers

Summary:
Ref T10939. Fixes T10181. This slightly simplifies, then documents the auditing rules, which haven't been updated for a while. In particular:

- If an owner authored the change, never audit.
- Examine all reviewers to determine reviewer audit status, not just the first reviewer.
- Simplify some of the loading code a bit.

Test Plan:
- Ran `bin/repository reparse --owners <commit> --force` to trigger this stuff.
- Verified that the web…