Integrate captions volume button with new CaptioningManager API

The code that checks for the captions service component will be removed
once the integration in the system captions side will happen.

Also cleans up the unused stream opt-out property.

Change-Id: I606f0d7a5319bbdc54b2e853fb70ea44ff9645a0
Bug: 221021539.
Bug: 136282740.
Test: Manually.