drm/xe: Faster devcoredump

The current algorithm to read out devcoredump is O(N*N) where N is the
size of coredump due to usage of the drm_coredump_printer in
xe_devcoredump_read. Switch to a O(N) algorithm which prints the
devcoredump into a readable format in snapshot work and update
xe_devcoredump_read to memcpy from the readable format directly.

v2:
 - Fix double free on devcoredump removal (Testing)
 - Set read_data_size after snap work flush
 - Adjust remaining in iterator upon realloc (Testing)
 - Set read_data upon realloc (Testing)
v3:
 - Kernel doc
v4:
 - Two pass algorithm to determine size (Maarten)
v5:
 - Use scope for reading variables (Johnathan)

Reported-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2408


Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240801154118.2547543-4-matthew.brost@intel.com