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

This reverts commit ec414dcb6c2f4bcbfad837a213d80ada7f854ed7.
Revert "sched/fair: Optimize find_busiest_queue()"

This reverts commit cbbed6ef6e12bd5122320afc20d166c7d1030f76.