ANDROID: sched: support pick_migrate_task in common kernel

__pick_migrate_task() was present in 5.10 and removed in
5.15 in favor of the balance_push concept.

Restore this function so that the ability to pick a task to migrate
across all scheduling classes can be used by vendor modules needed to
implement CPU Pause.

Function Removed In commit 1cf12e08
sched/hotplug: Consolidate task migration on CPU unplug

Bug: 205164003
Change-Id: I56ecd96c32b49495132daefbfc106568ab84e528
Signed-off-by: Stephen Dickey <quic_dickey@quicinc.com>
Signed-off-by: Ashay Jaiswal <quic_ashayj@quicinc.com>