UniFi - refactor entity management (#34367)

* Move removal of sensor entities into a base class

* Fix martins comments on sensors

* Reflect sensor changes on device_tracker platform

* Reflect sensor changes on switch platform

* Improve layering

* Make sure to clean up entity and device registry when removing entities

* Fix martins comments

homeassistant/components/unifi/controller.py

@@ -72,6 +72,8 @@ class UniFiController:
         self._site_name = None
         self._site_role = None
 
+        self.entities = {}
+
     @property
     def controller_id(self):
         """Return the controller ID."""