drm/xe/gt: Introduce runtime suspend/resume

drm/xe/gt: Introduce runtime suspend/resume

If power state is retained between suspend/resume cycle, we don't need
to perform full GT re-initialization. Introduce runtime helpers for GT
which greatly reduce suspend/resume delay.

v2: Drop redundant xe_gt_sanitize() and xe_guc_ct_stop() (Daniele)
    Use runtime naming for guc helpers (Daniele)
v3: Drop redundant logging, add kernel doc (Michal)
    Use runtime naming for ct helpers (Michal)
v4: Fix tags (Rodrigo)
v5: Include host_l2_vram workaround (Daniele)
    Reuse xe_guc_submit_enable/disable() helpers (Daniele)

Co-developed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Acked-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patch.msgid.link/20251030122357.128825-5-raag.jadav@intel.com