drm/xe/kunit: Add GuC Relay kunit tests

Add few tests to make sure that some negative and normal use
scenarios of the GuC Relay are implemented correctly.

Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://lore.kernel.org/r/20240104222031.277-10-michal.wajdeczko@intel.com
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>