Use the new Material Slider API in the Volume Dialog

This fix also enables the immediate steps animation using the new API

Flag: com.android.systemui.volume_redesign
Fixes: 394315097
Test: manual on the phone. Open the Volume Dialog and adjust the Volume
using buttons and dragging.

Change-Id: I3c154ecddbda6b01884f3dd7ea136a8009e6e40d