Switch Maniphest search indexing to real ApplicationTransactions

Summary:
Ref T2217. Move this off LegacyQuery and on to the real deal.

The rest of this patch mostly just replaces some gymnastics to get accurate-ish timestamps for CCs/Owners with time(). The search feature where edge time is stored was never really used and isn't necessarily of much value -- most indexers don't bother computing it exactly, and possibly we should get rid of it entirely. If it surfaces in the product again at some point, it's easy enough to make the time data more accurate and reindex.

Test Plan: Ran bin/search index T12, etc.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7069