Implemented function to get an icon name considering to OS color mode

For a Dark mode we start to looking of icons in folder "white"

Added missed "white" icons

src/slic3r/GUI/GUI_App.hpp

@@ -109,7 +109,6 @@ public:
 
     static unsigned get_colour_approx_luma(const wxColour &colour);
     static bool     dark_mode();
-    static bool     dark_mode_menus();
     void            init_label_colours();
     void            update_label_colours_from_appconfig();
     void            init_fonts();