drm/xe/pf: Add debugfs with scheduler groups information

drm/xe/pf: Add debugfs with scheduler groups information

Under a new subfolder, an entry is created for each group to list the
engines assigned to them. We create enough entries for each possible
group, with the disabled groups just returning an empty list.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patch.msgid.link/20251218223846.1146344-22-daniele.ceraolospurio@intel.com