- Sensor and text_sensor device_class tests now extract and verify the
packed argument is non-zero instead of just checking call presence
- Remove useless setup_test_environment fixture references in unit tests
* Add constants for sensor device_class
* Add device_class attribute to sensor component
* Add device_class attribute to sensor class
* Add device_class to mhz19 temperature sensor
* Add device_class to sensor in api component
* Add test for device_class of sensor
* Rename DEVICE_CLASS_NONE to DEVICE_CLASS_EMPTY for consistency
* Make optional attributes of sensor component truly optional