drm/xe/gt: Add APIs for printing stats over debugfs

drm/xe/gt: Add APIs for printing stats over debugfs

Add skeleton APIs for recording and printing various stats over
debugfs. This currently only added counter types stats which is backed
by atomic_t and wrapped with CONFIG_DRM_XE_STATS so this can be disabled
on production system.

v4: Rebase and other minor fixes (Matt)
v3: s/CONFIG_DRM_XE_STATS/CONFIG_DEBUG_FS(Lucas)
v2: add missing docs
    Add boundary checks for stats id and other improvements (Michal)
    Fix build when CONFIG_DRM_XE_STATS is disabled(Matt)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sai Gowtham Ch <sai.gowtham.ch@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240810191522.18616-1-nirmoy.das@intel.com
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>