R1:5cd13c3c65d0

Remove the last hardcoding from PhabricatorMetaMTAReceivedMail

Summary:
Moves all remaining mail handling into ReplyHandlers.

Farewell, `getPhabricatorToInformation()`! You were a bad method and no one liked you.

Ref T1205.

Test Plan:
- Used test console to send mail to Revisions, Tasks, Conpherences and Commits (these all actually work).
- Used test console to send mail to Requests, Macros, Questions and Mocks (these accept the mail but don't do anything with it, but didn't do anything before…