R1:0a3a3eae00e7

Modernize global search typeahead datasource

Summary: Ref T4420. Bring the global search up to date.

Test Plan: Typed various things into global search.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4420

Differential Revision: https://secure.phabricator.com/D9889