Turn On and Off actions integrated into Media Player

**Describe the problem you have/What new integration you would like**

Add Turn On and Turn Off as an optional trait in Media Player and then add as a configurable yaml option in Speaker/Media_Player.

**Please describe your use case for this integration and alternatives you've tried:**

I have external amp that I want to control and if setup correctly HA/MA would add button to GUI for player.

**Additional context**

Start by tracing the Media Player capability model and the Speaker/Media_Player YAML configuration mentioned in the request. Then check how player capabilities become controls in the GUI. Done means Turn On and Turn Off are optional, configurable actions and the corresponding player controls appear when enabled.

Written by the indexing model from the issue text.