Conpherence - finish basic application search

Summary:
Fixes T7584. Adds the ability to specify rooms, messages, or both. Adds policy icon to rooms result view and envelope icon to messages result view. Fixes a missing group by clause in thread query. Enforces having participant phid if the query isn't looking at rooms and doesn't have other particpant phids.

This last bit has a small UI quirk if the user searches for "messages" or "both" with no participant phids as we don't give them the feedback that they were included in the query. We could just slap the viewer in the particpants list in this case but it seemed like a buggier feeling experience to have the viewer appear up there? (Especially so in messages case, where we are basically being smart about policy filtering to come.)

Test Plan: clicked around and got sensible results

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7584

Differential Revision: https://secure.phabricator.com/D12232