While extending winevulkan<->win32u Unix interface is easy, I'm not convinced it's better long term. There are things that simply can be better inside win32u. For example, surface tracking: instead of a combination of `NtUserIsWindow` in winevulkan and drivers tracking windows and threads destruction, we could properly track it in window object, etc.
But yeah, things like tracking swapchain's physical device would need even more wrapping in win32u, so maybe when the time comes, it will make sense to just move majority of current `winevulkan/vulkan.c` to win32u. Anyway, it's nice to move more things out of drivers, I approved the MR.