Subclass most ReplyHandlers from TransactionReplyHandler
Summary: Ref T7199. Half of these aren't even reachable, but make some progress toward reducing the amount of nonsense and garbage in mail handling.
Test Plan: Tested all reachable handlers with bin/mail receive-test.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T7199
Differential Revision: https://secure.phabricator.com/D12237