This implementation of vkCmdSetEvent and vkCmdResetEvent assumes:
- There's only one queue (which currently is the case)
- Everything in the queue is executed linearly (which is currently the case)
- VkPipelineStageFlags can be ignored for now

Taking VkPipelineStageFlags into account could be used to avoid unnecessary
stalls or cache flushing. This will come at the optimization phase after
full conformance is achieved.

Bug b/117835459

Change-Id: Icb08a8b8e3fe63e827c9ba994a5e4353603e4ac9
Reviewed-on: https://swiftshader-review.googlesource.com/c/24371Tested-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>