sched/core: Relocate tg_get_cfs_*() and cpu_cfs_*_read_*()

Collect the getters, relocate the trivial interface file wrappers, and put
all of them in period, quota, burst order to prepare for future changes.
Pure reordering. No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250614012346.2358261-3-tj@kernel.org