Split pusher service send/request into unit.

Refactor sender's push destination handler.

Combine remnants of service::rooms::user with pusher service.

Further split and reorg pusher service units.

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/rooms/timeline/append.rs

@@ -168,7 +168,7 @@ where
 		.private_read_set(pdu.room_id(), pdu.sender(), *next_count2);
 
 	self.services
-		.user
+		.pusher
 		.reset_notification_counts(pdu.sender(), pdu.room_id());
 
 	let count = PduCount::Normal(*next_count1);