OpenXR Vulkan Example v1.2.0

Changelog:

• Updated OpenXR to v1.1.38. Note that API v1.0.38 is used for compatibility with some OpenXR runtimes.
• Adopted the XR_KHR_vulkan_enable2 OpenXR extension and replaced the outdated XR_KHR_vulkan_enable extension with it.
• Fixed how OpenXR frames that do not have the shouldRender flag set are handled. This fixes an issue where no rendering occurs when using the OpenXR-Vk-D3D12 interoperability layer.
• Added missing OpenXR swapchain image usage flags. This stops some validation errors from showing up.
• Fixed and optimized Vulkan render synchronization.
• Fixed resolution of Vulkan swapchain when it gets recreated.
• Added debug object names to a number of critical Vulkan resources when running in debug mode: draw and present queue(s), render pass, OpenXR swapchain images and command buffers. This makes it easier to tell application-owned and OpenXR runtime-owned resources apart and assists in debugging.
• Improved error detection and handling.

Thanks to @katz1 for reporting the OpenXR and Vulkan issues.