In preparation for moving display placement to win32u, for https://gitlab.winehq.org/wine/wine/-/merge_requests/551.
The idea for win32u to enumerate and work with full modes, with driver extra data, to do the display placement logic and validation, and pass the modes array for all adapters at once to the driver to apply them.
-- v3: winex11.drv: Constify set_current_mode DEVMODEW parameter. winex11.drv: Iterate display settings using dmDriverExtra. winex11.drv: Use DEVMODEW instead of x11drv_display_setting. winex11.drv: Update devmode dmPosition instead of new_rect. winex11.drv: Use DM_POSITION field bit to mark placed displays. winex11.drv: Use a local desired_rect variable when placing displays.