R1:332d787dc8f4

Support "Review Changes" and "Block Changes" settings for Owners package "Auto Review"

Summary:
Ref T10939. Fixes T8887. This enables and implements the "review" and "blocking review" options for packages.

This is a bit copy-pastey from `DifferentialReviewersHeraldAction`, which doesn't feel awesome. I think the right fix is Glorious Infrasturcture, though -- I filed T10967 to track that.

Test Plan:
- Set package autoreveiw to "Review".
- Updated, got a reveiwer.
- Set autoreview to "blocking".