audio: add call assistant usage

Add audio usage for call assistant use cases.
Used by apps playing over call uplink path for call
screening or other in call assitant features.
Add corresponding routing strategy in audio policy manager.
The strategy reuses volume group "PATCH" as volume is fixed
for call uplink audio.

Bug: 135213843
Test: make
Change-Id: Iad34c058e96fa5c969e825d3ddb0a82a60accc76