threading: assert valid instance/device in vkGet*ProcAddr
threading: assert valid instance/device in vkGet*ProcAddr

device is always valid in vkGetDeviceProcAddr.  instance is valid if pName
is not intercepted in layer_intercept_instance_proc.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools