[openxr] Handle OpenXR-specific Vulkan handle creation calls

[MarkY-LunarG]

OpenXR exposes several API calls that allow creation of Vulkan handles through it's API which will not go through the corresponding Vulkan calls.

These include:

• xrCreateVulkanInstanceKHR
• xrCreateVulkanDeviceKHR

In GFXR, we perform special work in the standard Vulkan calls that create instance and device handles that need to be replicated in the OpenXR paths. This includes state tracking, handle mapping, and device selection adjustments.