Revert "sched/fair: improve fairness efficiency"

This reverts commit afbfc594da86ad744a403eeb3270b3ba4581de7e.
Revert "sched/fair: Optimize cgroup pick_next_task_fair()"

This reverts commit c6e083511c0223d3a82ebc292d97e97aec6ac28a.
Revert "sched/fair: Optimize find_busiest_queue()"

This reverts commit 7acf7b96a64a8bf09c229bc95f3505aa3c6840b3.