account_popover: Use MenuModel + custom widget
GTK4 has recently added a way to insert custom widgets into menus created with a MenuModel. This allows for us to fully re-implement what we had in GTK3, which used ModelButtons.
GTK4 has recently added a way to insert custom widgets into menus created with a MenuModel. This allows for us to fully re-implement what we had in GTK3, which used ModelButtons.