R1:a27c824da67d

Draw project PHIDs from repositories when evaluating Herald object rules for commits

Summary:
Fixes T12097. In D16413, I simplified this code but caused us to load the //commit's// projects instead of the //repository's// projects, which is incorrect.

Normally, commits don't have any project tags when Herald evaluates, so using the commit's projects is generally meaningless.

Test Plan:
- Tagged a repository with `#X`.
- Created a Herald object rule for commits with `#X` as the object ("Always ... do…