tools/sched_ext: Receive updates from SCX repo

Receive tools/sched_ext updates form https://github.com/sched-ext/scx

 to
sync userspace bits:

- scx_bpf_dump_header() added which can be used to print out basic scheduler
  info on dump.

- BPF possible/online CPU iterators added.

- CO-RE enums added. The enums are autogenerated from vmlinux.h. Include the
  generated artifacts in tools/sched_ext to keep the Makefile simpler.

- Other misc changes.

Signed-off-by: Tejun Heo <tj@kernel.org>