R1:a592b32ca4b9

Share more code between tokenizers and global typeahead

Summary:
Ref T4420. Fixes T5306. Currently, the main menubar search has a lot of redundant/unshared code.

Move some common functions into `JX.Prefab.whatever()` and call them from the main search.

The major change here is that we apply the same "only show closed/disabled/archived objects if there are no matching open objects" logic, fixing T5306.

Test Plan:
- Used normal typeaheads.
- Used global search.
- Searched for a prefix shared by…