* Add definitions for grouping media players
See https://github.com/home-assistant/architecture/issues/364
* Fix Google Assistant tests
* Define sync versions of async_join_players/async_unjoin
* Don't use async API in synchronous test methods
* Fix tests and make pylint happy
The method name `unjoin` is used by another component, so let's use
`unjoin_player` instead.
* Fix emulated_hue tests
The new media player entity in the `demo` component requires a tiny
adjustment in the emulated_hue tests.
* Use "target:" in service description
* Also use "name:" in service descriptions
Co-authored-by: Franck Nijhof <git@frenck.dev>
