Dynamic MQTT connections (#3189)

* add mqtt-control
- adds auto-connect option to broker
- add new node mqtt-control
- adds i18n messages
- adds documentation

* documentation tweaks

* built in documentation improvements

* fix tip layout causing oversized editor

* remove unused requires

* add missing `unsubscribe` dropdown option
- oddly forgotten - now added

* ensure clientid is updated dynamically

* [rewrite] move mqtt-control login into mqtt-in

* Remove dynamic label

* remove redundant mqtt-control code left overs

* Callback for brokerConn.connect (improve done())
- done is now called on connect callback

* fix race condition if connect/disconnect too fast
- node.connected and node.client.connected getting out of sync

* fix connection fail when switching protocol 3 ~ 5
- ensure protocolId is correct for protocolVersion

* change msg.subscribe prop to `msg.topic`

* unsub all topics if msg.topic is `true`

* delete temprary debugger statements

* Final rework of dynamic mqtt connections

Co-authored-by: Steve-Mcl <sdmclaughlin@gmail.com>

packages/node_modules/@node-red/nodes/locales/en-US/messages.json

@@ -416,7 +416,11 @@
             "maximumPacketSize": "Max Packet Size",
             "receiveMaximum": "Receive Max",
             "session": "Session",
-            "delay": "Delay"
+            "delay": "Delay",
+            "action": "Action",
+            "staticTopic": "Subscribe to single topic",
+            "dynamicTopic": "Dynamic subscription",
+            "auto-connect": "Connect automatically"
         },
         "sections-label":{
             "birth-message": "Message sent on connection (birth message)",
@@ -457,7 +461,10 @@
             "invalid-topic": "Invalid topic specified",
             "nonclean-missingclientid": "No client ID set, using clean session",
             "invalid-json-string": "Invalid JSON string",
-            "invalid-json-parse": "Failed to parse JSON string"
+            "invalid-json-parse": "Failed to parse JSON string",
+            "invalid-action-action": "Invalid action specified",
+            "invalid-action-alreadyconnected": "Disconnect from broker before connecting",
+            "invalid-action-badsubscription": "msg.topic is missing or invalid"
         }
     },
     "httpin": {