The new Night Light page, as described by the latest mockups [1],
uses a listbox to display the options. Also, there is a small
revamp on how the disabled state is handled; it now is a switch
in a row, instead of an extra radio button.
This commit changes the Night Light page to have a listbox, and
uses libhandy's rows to achieve the desired interface.
Fixes https://gitlab.gnome.org/GNOME/gnome-control-center/issues/533