* Add turn_on/off to camera
* Add turn_on/off supported features to camera.
Add turn_on/off service implementation to camera, add turn_on/off
supported features and services to Demo camera.
* Add camera supported_features tests
* Resolve code review comment
* Fix unit test
* Use async_add_executor_job
* Address review comment, change DemoCamera to local push
* Rewrite tests/components/camera/test_demo
* raise HTTPError instead return response