Handle SCO volume commands like any absolute volume device

If the unify_absolute_volume_management flag is enabled prefer checking
first if the device type has been registered as an absolute volume
device through the AudioDeviceVolumeManager API and proceed with the
unified absolute volume handling.

Flag: android.media.audio.unify_absolute_volume_management
Bug: 393657380
Test: atest audiopolicy_tests

Change-Id: Ic8c5e698094769eb260c15b836975a3910714fdc