R1:ddfc6bbc9e5c

Service "Group by: Project" in Maniphest out of a local index

Summary:
See discussion in D6955. Currently, the logic for "Group by: Project" is roughly:

- Load every possible result.
- Lots of in-process garbage.

Instead, use the new local project name index (from D6957) to service this query more reasonably. Basically:

- Join a table which has keyed project names.
- Order by that table.

Test Plan: {F58033}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https…