Add gtk4 list models
From upstream commit 0ef0edfa9a9bb6c1bb25cf5742f3d61afed8e001.
Newer commits were more difficult to incorporate because the sources included in gtk/roaring were spewing tons of warnings/errors.
We will get rid of this folder once we switch to Gtk4 down the line so it shouldn't be a problem.
Split out from !466 (closed) because that allows to use the list models outside of the history as well (manager could f.e. use GtkFlattenListModel
for the origins).