ANDROID: cgroup: Add android_rvh_cgroup_force_kthread_migration

In Android GKI, CONFIG_FAIR_GROUP_SCHED is enabled [1] to help
prioritize important work. Given that CPU shares of root cgroup
can't be changed, leaving the tasks inside root cgroup will give
them higher share compared to the other tasks inside important
cgroups. This is mitigated by moving all tasks inside root cgroup to
a different cgroup after Android is booted. However, there are many
kernel tasks stuck in the root cgroup after the boot.

It is possible to relax kernel threads and kworkers migrations under
certain scenarios. However the patch [2] posted at upstream is not
accepted. Hence add a restricted vendor hook to notify modules when a
kernel thread is requested for cgroup migration. The modules can relax
the restrictions forced by the kernel and allow the cgroup migration.

[1] https://android.googlesource.com/kernel/common/+/f08f049de11c15a4251cb1db08cf0bee20bd9b59
[2] https://lore.kernel.org/lkml/1617714261-18111-1-git-send-email-pkondeti@codeaurora.org



Bug: 184594949
Bug: 301261126
Change-Id: I445a170ba797c8bece3b4b59b7a42cdd85438f1f
Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
[quic_dickey@quicinc.com: port to android-mainline kernel]
Signed-off-by: Stephen Dickey <quic_dickey@quicinc.com>
(cherry picked from commit 7551a1a2)