After Aphlict reconnects, ask the server to replay recent messages
Fixes T12563. If we've ever seen an "open", mark all future connections as reconnects. When we reconnect, replay recent history.
(Until duplicate messages (T12564) are handled better this may cause some notification duplication.)
Also emit a reconnect event (for T12566) but don't use it yet.
Reviewed By: chad
Maniphest Tasks: T12563
Differential Revision: https://secure.phabricator.com/D17708