Use the gtk/menus.ui resource to automatically populate the menubar for all GtkApplicationWindow's
Review Request #1239 — Created Jan. 17, 2022 and submitted — Latest diff uploaded
I didn't port any of the dynamic menus from the buddy list yet, so the Buddy List window currently has two menu bars, but none of the items are duplicated.
Compiled and verified that all of the menu items that were moved continue to function.
Also ran on mac and verified that the new menubar stuff was properly shown and functional at the top of the screen.