Both stack pages are merged into one page to avoid additional cycling through pages. `GtkListBoxRow`s were replaced by `AdwActionRow`s with `GtkCheckBox`es as children. Closes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/90, https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1003 Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/362>