Overview of changes
- Be forgiving of a missing /etc/profile.d/toolbox.sh in 'run'
- Don't sanity check /etc/subgid and /etc/subuid when running as root
- Install only flatpak-spawn, not the rest of flatpak-xdg-utils, in the images
- Let the terminal know the active container only on some Fedora variants
- Rely on 'podman system migrate' always being present
- Simplify code by dropping compatibility with 'podman create' < 1.4.0
- Switch to using /usr/lib/os-release instead of /etc/os-release
- Unbreak 'create' on Silverblue
- Update default release to 30 when running on non-fedora hosts