ANDROID: sched: Push execution and scheduler context split into deadline and rt

In preparation for chain migration, push the awareness
of the split between execution and scheduler context
down into some of the rt/deadline code paths that deal
with load balancing.

This patch was broken out from a larger chain migration
patch originally by Connor O'Brien.

Cc: Joel Fernandes <joelaf@google.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Metin Kaya <Metin.Kaya@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: kernel-team@android.com
Change-Id: Ie71af403e471c201f4eb8a65fe422e738b51d61b
Signed-off-by: Connor O'Brien <connoro@google.com>
[jstultz: split out from larger chain migration patch]
Signed-off-by: John Stultz <jstultz@google.com>
Bug: 306081722
---
v8:
* Move null exec_ctx check to a later patch, as suggested by
  Metin
v9:
* Folded down cpupri null check changes from later patch, as
  suggested by Metin