Change state_information to return feature values (#804)

This changes `state_information` to return the names and values of
all defined features.
It was originally a "temporary" hack to show some extra, device-specific
information in the cli tool, but now that we have device-defined
features we can leverage them.

kasa/device.py

@@ -304,9 +304,9 @@ class Device(ABC):
         """Return all the internal state data."""
 
     @property
-    @abstractmethod
     def state_information(self) -> Dict[str, Any]:
-        """Return the key state information."""
+        """Return available features and their values."""
+        return {feat.name: feat.value for feat in self._features.values()}
 
     @property
     def features(self) -> Dict[str, Feature]: