Unprototype the Ferret UI fields

Summary:
Ref T12819. Show the new Ferret engine fields (and enable the indexer) unconditionally.

Also pull them to the top since they're fairly general-purpose and appear more broadly now, and also they actually work correctly (WOW).

Some redundant fields (like "Name Contains" in Repositories and Owners) could probably be removed now, I may clean those up in a followup.

Test Plan: Browsed around, saw Ferret fields in UI without "(Prototype)" suffix.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12819

Differential Revision: https://secure.phabricator.com/D18587