R1:4bf968148cb8

Fix pagination of fulltext search results

Summary:
Fixes T8285. Fulltext search relies on an underlying engine which can not realistically use cursor paging. This is unusual and creates some oddness.

Tweak a few numbers -- and how offsets are handled -- to separate the filtered offset and unfiltered offset.

Test Plan:
- Set page size to 2.
- Ran a query.
- Paged forward and backward through results sensibly, seeing the full result set.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T8285…