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
This is a massive rewrite of the panel. Because we can't have
nice things and WebKit2GTK for GTK4 won't be ready in time,
rework the panel to spawn a new subprocess with a dialog that
handles online accounts - both creation and editing.
