drm/xe: Add HW Engine snapshot to xe_devcoredump.

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

v2: remove unnecessary, and now duplicated, dma_fence annotation. (Matthew)
v3: avoid for_each with faulty_engine since that can be already freed at
    the time of the read/free. Instead, iterate in the full array of
    hw_engines. (Kasan)

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