Add muting/unmuting when volume change to/from min value

Also fix setting a11y description because in the VolumeSlider. We should
always set progressbar info to allow a11y gestures to change the value.

Flag: aconfig new_volume_panel NEXTFOOD
Test: atest AudioVolumeInteractorTest
Test: manual on the device with the voiceover
Fixes: 339162398
Change-Id: I13e0aad3325edd6d16ad5a9b9aaa5dc79db3c21c