Fix set_state for common light modules (#929)

PR contains a number of fixes from testing with HA devices:

- Fixes a bug with turning the light on and off via `set_state`
- Aligns `set_brightness` behaviour across `smart` and `iot` devices
such that a value of 0 is off.
- Aligns `set_brightness` behaviour for `IotDimmer` such that setting
the brightness turns on the device with a transition of 1ms. ([HA
comment](https://github.com/home-assistant/core/pull/117839#discussion_r1608720006))
- Fixes a typing issue in `LightState`.
- Adds `ColorTempRange` and `HSV` to `__init__.py`
- Adds a `state` property to the interface returning `LightState` for
validating `set_state` changes.
- Adds tests for `set_state`

kasa/smart/modules/light.py

@@ -14,6 +14,8 @@ from ..smartmodule import SmartModule
 class Light(SmartModule, LightInterface):
     """Implementation of a light."""
 
+    _light_state: LightState
+
     def query(self) -> dict:
         """Query to execute during the update cycle."""
         return {}
@@ -131,9 +133,34 @@ class Light(SmartModule, LightInterface):
         """Set the light state."""
         state_dict = asdict(state)
         # brightness of 0 turns off the light, it's not a valid brightness
-        if state.brightness and state.brightness == 0:
+        if state.brightness == 0:
             state_dict["device_on"] = False
             del state_dict["brightness"]
+        elif state.light_on is not None:
+            state_dict["device_on"] = state.light_on
+            del state_dict["light_on"]
+        else:
+            state_dict["device_on"] = True
 
         params = {k: v for k, v in state_dict.items() if v is not None}
         return await self.call("set_device_info", params)
+
+    @property
+    def state(self) -> LightState:
+        """Return the current light state."""
+        return self._light_state
+
+    def _post_update_hook(self) -> None:
+        if self._device.is_on is False:
+            state = LightState(light_on=False)
+        else:
+            state = LightState(light_on=True)
+            if self.is_dimmable:
+                state.brightness = self.brightness
+            if self.is_color:
+                hsv = self.hsv
+                state.hue = hsv.hue
+                state.saturation = hsv.saturation
+            if self.is_variable_color_temp:
+                state.color_temp = self.color_temp
+        self._light_state = state