drm/xe/guc: Add GuC log to devcoredump captures

Include the GuC log in devcoredump captures because they can be useful
with debugging certain types of bug.

v2: Fix kerneldoc
v3: Drop module parameter as now using more compact ascii85 encoding
rather than hexdump (although still not compressed) (review feedback
from Matthew B). Rebase onto recent refactoring of devcoredump code.
v4: Don't move the submission snapshot inside the GuC internals
structure 'cos it really doesn't belong there.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Julia Filipchuk <julia.filipchuk@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003004611.2323493-11-John.C.Harrison@Intel.com