This does the same as https://gitlab.winehq.org/wine/wine/-/merge_requests/6398 but for Vulkan. It also implements vulkan child window rendering pretty much for free and supersedes https://gitlab.winehq.org/wine/wine/-/merge_requests/5573.
It is not completely optimal and there as missed opportunities to keep child windows on screen when no DPI scaling and no cropping is needed, but it would require to be smarter and have knowledge about the window clipping region, which will probably better be done in win32u. This is exactly the same for OpenGL, and it will probably be solved together.
-- v2: winex11: Implement vulkan DPI scaling and child window rendering. winex11: Only update the client window position in sync_client_position. winex11: Update the GL client window size when it is presented. winex11: Update the vulkan surface size when it is presented. winex11: Use a dedicated structure for vulkan surface private data. win32u: Pass vulkan driver private data to vulkan_surface_presented. winevulkan: Use client rect in window DPI instead of monitor DPI.