Update interfaces so they all inherit from Device (#893)

Brings consistency to the api across Smart and Iot so the interfaces can be used for their specialist methods as well as the device methods (e.g. turn_on/off).

kasa/device.py

@@ -245,6 +245,11 @@ class Device(ABC):
         """Return  True if the device is dimmable."""
         return False
 
+    @property
+    def is_fan(self) -> bool:
+        """Return True if the device is a fan."""
+        return self.device_type == DeviceType.Fan
+
     @property
     def is_variable_color_temp(self) -> bool:
         """Return True if the device supports color temperature."""