drm/xe: Add GuC CT snapshot to xe_devcoredump.

Let's start to move our existent logs to devcoredump one by
one. Any format change should come on follow-up work.

v2: Rebase and add the dma_fence locking annotation here.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>