Always schedule configure on maximize and fullscreen requests

This is my approach for fixing #2330 (closed). The idea is that compositors already implement handlers that call these functions (probably), so wlroots should do the "right thing" and always schedule a configure event even if the compositor decided not to change the window state.

If a compositor like sway doesn't care about maximize requests, it still needs to implement a stub handler that calls set_maximized to indicate it is done considering the request.