Fix NVIDIA-specific black screen/inverted colors when streaming via Steam Remote Play atop gamescope.

[cmspam]

These changes detect the NVIDIA proprietary driver via VkPhysicalDeviceDriverProperties and apply two fixes for Steam Remote Play with Gamescope (running steam within gamescope, in 'deck mode' for example):

1. Black screen fix: The screenshot texture was not marked as bSampled, which is required for the RGB-to-NV12 conversion shader to sample it on NVIDIA. This caused a black screen when streaming via Remote Play.
2. Inverted R/B colour fix: Once the black screen was resolved, it was discovered that sampling VK_FORMAT_A2R10G10B10_UNORM_PACK32 storage images on the NVIDIA proprietary driver returns the R and B channels swapped in the shader. When the proprietary driver is detected, DRM_FORMAT_XBGR2101010 is used instead of DRM_FORMAT_XRGB2101010 for the RGB capture texture, so the components arrive in the correct order.

Neither fix affects mesa or other vendors.

I have also submitted this PR upstream, but since bazzite is fast-moving and has dedicated NVIDIA deck images, I think it would potentially be appropriate and helpful to users, to include this fix.

Upstream PR is here:
ValveSoftware#2094