ci: Various fixes
To hopefully fix build errors in containers which we see at !671 (merged)
Done here:
- Update to latest ci-templates
- Allow failure for fedora-rawhide@aarch64 build
- Update Fedora build instructions for DNF5 package manager
- Use Debian Stable instead of Ubuntu, as the Ubuntu image does not work with the ci-templates (i think because it has multiple user accounts, and the ci-templates use rootless podman in a way that it can only deal with files owned by 'root' in the container)
Edited by Sam Thursfield