WIP: vulkan: Common (I hope!) YCbCr conversion code

This MR is yet another on the train towards common Vulkan code. This time, trying to tackle YCbCr conversion. There are two new common bits:

1. A new common vk_ycbcr_conversion struct with vk_common_Create/Destroy implementations
2. A new common NIR pass for lowering away YCbCr conversions. I think this will work for ANV and RADV but am less sure about mobile drivers as they may have actual hardware for this stuff.

This is WIP because, while it does work for ANV, there are some ToDo items which I'll make clear in discussion comments below.

Closes: #4543