drm/xe: Add helper to accumulate exec queue runtime

drm/xe: Add helper to accumulate exec queue runtime

Add a helper to accumulate per-client runtime of all its
exec queues. This is called every time a sched job is finished.

v2:
  - Use guc_exec_queue_free_job() and execlist_job_free() to accumulate
    runtime when job is finished since xe_sched_job_completed() is not a
    notification that job finished.
  - Stop trying to update runtime from xe_exec_queue_fini() - that is
    redundant and may happen after xef is closed, leading to a
    use-after-free
  - Do not special case the first timestamp read: the default LRC sets
    CTX_TIMESTAMP to zero, so even the first sample should be a valid
    one.
  - Handle the parallel submission case by multiplying the runtime by
    width.
v3: Update comments

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240517204310.88854-6-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>