R1:bdd1edea7a40

Modernize ManiphestTask paging and ordering

Summary:
Ref T7803. The ApplicationSearch integration is still a little rough here, but it seems to have the correct behavior.

The rest of this is now at least relatively sane, cohesive, and properly behaved.

Test Plan:
- Used all grouping and ordering queries in Maniphest. Pagingated results.
- Used custom field ordering in Maniphest. Paginated results.
- Paginated through the `null` section of "Assigned" and "Projects" group-by queries. Pagingation now…