R1:06fc82a3eeff

Mark reviewers as "commented" when they leave a comment

Summary:
Ref T2222. This requires one new trick:

- When merging edge transactions which both add/update an edge, the Editor gets to control how the edge data is merged.

Specifically, we pick the "strongest" state to keep, so "accept + comment" leaves you with an accept instead of a comment.

Test Plan: Accepted, commented on, and comment + accepted revisions. Added some debugging dumps to verify that the merging was getting hit and working…