Do not use pychromecast.Chromecast for Cast Groups (#8786)

* Do not use pychromecast.Chromecast for Cast Groups

pychromecast.Chromecast creates Chromecast instance with friendly_name and cast_type of the device and not of a group.
Which leads to collisions

* Update cast.py

* using hass.data

* Fixed and extended tests

* Line length in tests

* Lint in tests