Make AmbientVolumeSlider compatible with a11y services

1. Prevent accessibility services focus on no-action view
2. Enable setting the content description on the slider

Flag: EXEMPT bugfix
Bug: 397355964
Bug: 397355156
Bug: 397354989
Bug: 397134669
Test: manually test with Voice Access/Switch Access/TalkBack
Change-Id: If0c40d7b91061da5e100e49e71279adb6f69e77f