Rename the app-id to org.gnome.Settings since this is what
we've been calling it for many years now. Adjust all files
that derive from the app-id, such as the desktop file, D-Bus
service file names, search providers, GSettings schemas, to
match that.
Closes https://gitlab.gnome.org/GNOME/gnome-control-center/-/issues/344
Boy this was hard.
To ease the pain of porting wireless-security to GTK4, add
a new WsFileChooserButton class that mimics the behavior of
a button that triggers a filechooser, as per the migration
guide suggests.
There were lots of GtkGrids, so the diff is particularly
horrendous. Sorry.
This needs serious testing before landing.
