Update volume control ui for tv

As part of this we introduce a new theme "volume_dialog_theme", which
in the general case is the same as the previously used "qs_theme". Just
for TVs we override the accentColor.

Before: https://hsv.googleplex.com/5706562045739008
After: https://hsv.googleplex.com/5373850558660608

Bug: 162302410
Test: flash on atv device && press +/- on remote
Change-Id: I1151746cf417effbb300c0c11a26b8f75e9d8fb2