R1:809c7bf996af

Allow users to manage package dominion rules

Summary: Ref T10939. This adds UI, transactions, etc, to adjust dominion rules.

Test Plan:
- Read documentation.
- Changed dominion rules.
- Created packages on `/` ("A") and `/x` ("B") with "Auto Review: Review".
- Touched `/x`.
- Verified that A and B were added with strong dominion.
- Verified that only B was added when A was set to weak dominion.
- Viewed file in Diffusion, saw correct ownership with strong/weak dominion rules.

Reviewers…