Vulkan Renderer using VK_KHR_video_decode_h264 and VK_KHR_video_decode_h265

[KWottrich]

Is your feature request related to a problem? Please describe.
Moonlight and Sunshine do not support 4:4:4 chroma subsampling, which is partly due to poor hardware support for 4:4:4 decoding. The Vulkan extensions for video decoding (VK_KHR_video_decode_h264 and VK_KHR_video_decode_h265) do support 4:4:4 decoding, meaning that a Vulkan renderer supporting VK_VIDEO_CHROMA_SUBSAMPLING_444_BIT_KHR would open the door for hardware-accelerated 4:4:4 subsample decoding support for any device whose driver supports the corresponding Vulkan extensions.

Describe the solution you'd like

• Add a Vulkan renderer with support for VK_KHR_video_decode_h264 and VK_KHR_video_decode_h265 alongside DXVA2 and D3D11VA on Windows.
• Add a Vulkan renderer with support for VK_KHR_video_decode_h264 and VK_KHR_video_decode_h265 alongside VAAPI, VDPAU, and NVDEC on Linux.
• (MacOS does not support Vulkan directly, and MoltenVK does not appear to support VK_KHR_video_decode_h264 or VK_KHR_video_decode_h265)

Describe alternatives you've considered
The only other game streaming solution with support for 4:4:4 chroma subsampling is a premium subscription for Parsec Warp.

Additional context
Discussion about hardware support limitations for hardware encoding/decoding video streams with 4:4:4 subsampling on the Sunshine GitHub page: https://github.com/LizardByte/Sunshine/discussions/1188

[cgutman]

There is already a Vulkan renderer that supports VK_KHR_video_decode_h264, VK_KHR_video_decode_hevc, and VK_KHR_video_decode_av1 in Moonlight v6.0.0. It is shipping for Linux in v6.0 but will also ship for Windows in v6.1 for YUV 4:4:4. See also #1282