R1:9434df9d7cdd

Accommodate project reviewers in Differential search

Summary:
Ref T1279. Two changes to the search/query for Differential:

- "Reviewers" now accepts users and projects.
- "Responsible Users" now includes revisions where a project you are a member of is a reviewer.

Test Plan:
- Searched for project reviewers.
- Verified that the dashboard now shows reviews which I'm only part of via project membership.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1279

Differential…