Port to GTK4
This will be done in three phases:
- Plain port to GTK4 (not much visual difference, available in https://gitlab.gnome.org/GNOME/shotwell/-/tree/wip/gtk4)
- Replace or fix the checkerboard view to not use old-style Cairo rendering (gives already issues with medium-sized libraries)
- Visual revamp including move to LibAdwaita
Edited by Jens Georg