Revert "sched/fair: Optimize cgroup pick_next_task_fair()"

This reverts commit fbc5bdcefd5cd9daa1330199febe30431ad5b9ff.
Revert "sched/fair: Optimize find_busiest_queue()"

This reverts commit 05f2c9bb694edaa43368f999f1821ea550abe757.