Make the "Add Auditors" Herald rules use modern transactions

Summary:
Ref T10978. Convert "Add Auditors" rules in Herald to modern modular transactions.

Here and in D17262 (and in the next change), I've removed "audit reasons". There are several reasons for this:

• They're pretty hacky.
• They store English-language (well, usually) text in the database, which can't be translated.
• I think they may not be necessary. When they were written, Herald did not apply transactions, so it was less clear when Herald was doing something. In modern code, it does, so Herald auditors are clear. The owenrs/package rules are now more clear, too. I'd like to see evidence that confusion still exists before rebuilding this feature in a modern, translatable way, since I think we may not need it at all.

Test Plan: Ran bin/repository reparse --herald <commit> to re-run Herald rules. Saw rules add auditors appropriately.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10978

Differential Revision: https://secure.phabricator.com/D17263