R1:d6bce34a5db1

Update Conpherence to use EditEngine

Summary: Moves Conpherence to use EditEngine. This removes the "First Message" field, but I think that's ok until we have direct messaging of some sort, then maybe have built-ins cover that case.

Test Plan:
- Visit /new/ and /edit/ for creating new rooms.
- Edit a room in full conpherence
- Edit a room in durable column
- grep for METADATA calls

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T11729

Differential Revision…