add a test for semaphore payloads that are ignored

[bashbaug]

The spec currently says for the sema_payload_list that may be passed to clEnqueueWaitSemaphoresKHR and clEnqueueSignalSemaphoresKHR:

sema_payload_list points to the list of values of type cl_semaphore_payload_khr containing valid semaphore payload values to wait on. This can be set to NULL or will be ignored when all semaphores in the list of sema_objects are of type CL_SEMAPHORE_TYPE_BINARY_KHR.

Even if this wording changes slightly - see https://github.com/KhronosGroup/OpenCL-Docs/pull/1362#discussion_r2070804827 - it looks like we're currently always passing NULL as our semaphore payload list. We should add some targeted testing to ensure that a non-NULL semaphore payload list is properly accepted and that it is ignored.