R1:a2a2b3f7f4b5

Sort global fulltext results by overall relevance

Summary:
Ref T12819. Currently, under the Ferret engine, we query each application's index separately and then aggregate the results.

At the moment, results are aggregated by type first, then by actual rank. For example, all the revisions appear first, then all the tasks.

Instead, surface the internal ranking data from the underlying query and sort by it.

Test Plan: Searched for "A B" with a task named "A B" and a revision named "A". Saw task first.