Add libprocessgroup dependency and fix sched_policy include

libaudioclient and libmedia are using get_sched_policy and
set_sched_policy which are now implemented inside libprocessgroup.
Add required dependencies and include required headers.

Exempt-From-Owner-Approval: janitorial

Bug: 111307099
Test: builds, boots

Merged-In: I83dd6878839122e3ea71b7be6f6f312376897d56
Change-Id: I83dd6878839122e3ea71b7be6f6f312376897d56
Signed-off-by: Suren Baghdasaryan <surenb@google.com>