Refactor MQTT (#24010)

* refactor mqtt so that Frigate owns the transport lifecycle instead of delegating it to paho

* release the shutdown barrier on worker crash and replay retained publishes the broker never acked

* collapse in-flight retained values by topic and release the shutdown barrier from a finally

* replay the outage buffer before the publish queue so newer values are not reverted

frigate/comms/ws.py

@@ -466,7 +466,6 @@ class WebSocketClient(Communicator):
 
     def subscribe(self, receiver: Callable) -> None:
         self._dispatcher = receiver
-        self.start()
 
     def start(self) -> None:
         """Start the websocket client."""