debian11, debian12: add missing qcow2 images
All architectures and variants for Debian 11 and Debian 12 should now be included. For details, see
Debian Official Cloud Images https://cloud.debian.org/
Debian 12 images https://cloud.debian.org/images/cloud/bookworm/latest/
Debian 11 images https://cloud.debian.org/images/cloud/bullseye/latest/
Image links checked with pytest --log-cli-level=INFO --network-tests -k 'test_urls[debian12] or test_urls[debian11]'
Signed-off-by: Anmol Khirbat anmol@khirbat.net