Add libprocessgroup dependency and fix sched_policy include

libbt-utils uses set_sched_policy which is now implemented inside
libprocessgroup. Add required dependency and header file include.

Exempt-From-Owner-Approval: janitorial

Bug: 111307099
Test: builds, boots

Merged-In: I4d0dcfad22b30ac249a7874b42a7121e2ffedadb
Change-Id: I4d0dcfad22b30ac249a7874b42a7121e2ffedadb
Signed-off-by: Suren Baghdasaryan <surenb@google.com>