tools/sched: Add root_domains_dump.py which dumps root domains info

tools/sched: Add root_domains_dump.py which dumps root domains info

Root domains information is somewhat hard to access at runtime. Even
with sched_debug and sched_verbose, such information is only printed
on kernel console when domains are modified.

Add a simple drgn script to more easily retrieve root domains
information at runtime.

Since tools/sched is a new directory, add it to MAINTAINERS as well.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> # nuc & rock5b
Link: https://lore.kernel.org/r/20250627115118.438797-5-juri.lelli@redhat.com