Don't use C++ callback to notify close request from Qt Figures (bug #54187) * Figure.h/cc (Figure::close_figure_callback): Remove callback. (Figure::eventNotifyBefore): Use gh_manager::post_callback rather than octave_link::post_event to notify that a figure should be closed. * graphics.in.h (graphics_event::create_mcode_event): New static function. * graphics.cc (mcode_event): New class to handle direct mcode evaluation. (gh_manager::do_post_callback): For "closerequestfcn" callback, create an mcode_event and use the "close" function to make the figure current before evaluating the actual closerequestfcn.