Unify slider control between Volume Panel and Volume Dialog

The new Volume Dialog and Volume Panel will both use the same Slider
control, that handles haptics, a11y and animated snapping. This change
mostly copies the VolumeSlider used in the Volume Panel and adapts it
for the Volume Dialog.

Flag: com.android.systemui.volume_redesign
Fixes: 393133850
Fixes: 395578673
Test: atest VolumeDialogScreenshotTest
Test: atest VolumePanelScreenshotTest
Test: manual on foldable
Change-Id: I31fb77d391f7da78c18cc70e7da8a87f84f6c0fc