drm/xe: Add ctx timestamp to LRC snapshot

The ctx timestamp is useful information, add to LRC snapshot.

v2:
  - s/ctx_timestamp_job/ctx_job_timestamp

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240611144053.2805091-5-matthew.brost@intel.com