The class implements a menu item that contains a section which
can be collapsed into a submenu.
It is very common for network devices to only have one associated
connection, so hiding away a single item in a submenu is fairly
inconvenient.
This class will address this, by only using a submenu when it is
actually needed.
Although the main issue it addresses is that menus (including
sections) aren't GObjects. This gives us a GObject that can
be added to a menu, and that can itself contain other menu
items.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2407>
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