Bugfix: Ring volume stuck at zero on tangor

Solution: offer a boolean config for volumeUpToExitSilent and
overwrite it for tangorpro.

Flag: NONE
Bug: b/279645379
Test: Manual. Slide ring volume all the way left in settings.
Press volume up. Ring volume slider progress should move away from 0,
and the ring icon should change from silent to normal.

Change-Id: Ice564acc8226d5baa6059bf3d9c34ffc0111f4d1