Preparation for https://gitlab.winehq.org/wine/wine/-/merge_requests/6323
-- v3: winewayland: Detach client surfaces when they are not visible. winewayland: Move client surface to wayland_win_data struct. winewayland: Pass hwnd to and return client rect from wayland_surface_get_client. winewayland: Introduce a new wayland_client_surface_attach helper. winewayland: Move wayland_surface_get_client to window.c.