Revert "sched: pack the idle load balance"

This reverts commit 0eaf63829d934cb4a28cc471ee6b51f61ff2e7f8.
Revert "sched: secure access to other CPU statistics"

This reverts commit 65100d8c19ea2f9f49f732e46dc1ed1fb8b69256.
Revert "sched: pack small tasks"

This reverts commit 791008d4a103c8c7d43de845e8f74366bfdd30b6.