drm/xe/guc: Track FAST_REQ H2Gs to report where errors came from

drm/xe/guc: Track FAST_REQ H2Gs to report where errors came from

Most H2G messages are FAST_REQ which means no synchronous response is
expected. The messages are sent as fire-and-forget with no tracking.
However, errors can still be returned when something goes unexpectedly
wrong. That leads to confusion due to not being able to match up the
error response to the originating H2G.

So add support for tracking the FAST_REQ H2Gs and matching up an error
response to its originator. This is only enabled in XE_DEBUG builds
given that such errors should never happen in a working system and
there is an overhead for the tracking.

Further, if XE_DEBUG_GUC is enabled then even more memory and time is
used to record the call stack of each H2G and report that with the
error. That makes it much easier to work out where a specific H2G came
from if there are multiple code paths that can send it.

v2: Some re-wording of comments and prints, more consistent use of #if
vs stub functions - review feedback from Daniele & Michal).
v3: Split config change to separate patch, improve a debug print
(review feedback from Michal).
v4: Bunch of minor tweaks (review feedback from Michal).

Original-i915-code: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20250512215324.1457009-5-John.C.Harrison@Intel.com