Vulkan memory model: semantics validation

Ban sequentially consistent with VulkanKHR

* Added validation check that SequentiallyConsistent memory semantics
are not used if the memory model is VulkanKHR
 * Added tests
* Fixed a bug in evaluating constant 32-bit integers and updated some
handling to avoid inferring a value from a spec constant default

Remaining memory semantics validation

* Adds checks that OutputMemoryKHR, MakeAvailableKHR and MakeVisibleKHR
are only used if the VulkanMemoryModelKHR capabailty is present
* Added checks that MakeAvailableKHR requires release semantics
* Added checks that MakeVisibleKHR requires acquire semantics
* Added checks that MakeAvailableKHR and MakeVisibleKHR require a
storage class