The Screen Sharing dialog used to have a switch, which was changed to a
checkbox in 8b68961431
However, unlike switches, checkboxes are expected to have clicable labels
Let's set the label properly, instead of doing it the switch way.
Fixes https://gitlab.gnome.org/GNOME/gnome-control-center/-/issues/565
Put the widget's content into a HdyColumn, itself into a
GtkScrolledWindow. This allows the panel to reach narrower sizes.
This deliberately doesn't adapt the indentation of the contained widget
to help this commit to be more readable and easier to review, it will be
adapted in the next commit.