drm/xe: Use GT TLB invalidation jobs in PT layer

Rather than open-coding GT TLB invalidations in the PT layer, use GT TLB
invalidation jobs. The real benefit is that GT TLB invalidation jobs use
a single dma-fence context, allowing the generated fences to be squashed
in dma-resv/DRM scheduler.

v2:
 - s/;;/; (checkpatch)
 - Move ijob/mjob job push after range fence install
v3:
 - Remove extra newline (Stuart)
 - Set ijob/mjob near creation (Stuart)
 - Add comment back in (Stuart)

Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://lore.kernel.org/r/20250724191216.4076566-7-matthew.brost@intel.com