[Flatpak] Use GtkFileChooserNative for Flatpak portals support
In order to use the flatpak filesystem access portals you need to switch from using GTKFileChooser to GTKFileChooserNative. This should be basically seamless, unless adding buttons or widgets to the dialog is required.
This upstreams the following bug report from Flathub: https://github.com/flathub/org.gnome.Evolution/issues/2
Edited by Milan Crha