sched/fair: Add related data structure for task based throttle

Add related data structures for this new throttle functionality.

Tesed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Aaron Lu <ziqianlu@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Matteo Martelli <matteo.martelli@codethink.co.uk>
Link: https://lore.kernel.org/r/20250829081120.806-2-ziqianlu@bytedance.com