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 open and archived projects, didn't see the archived ones until the open ones were exhausted.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5306, T4420

Differential Revision: https://secure.phabricator.com/D9899