SchedulingPolicyService: specify the beneficiary of priority boost

audioflinger needs to request priority boost on behalf of hal.
This way, a new use case is introduced for requestPriority call.

Bug: 34131400
Change-Id: I6cd0e509da2b0166ca4fce181287584179abe391
Test: check priority match between audioflinger's and hal's threads
2 files changed