diskimage-builder configs for cloud image build automation

Create a virtual environment .venv in this directory and install python-openstackclient and diskimage-builder. Add a clouds.yaml file with administrative rights to push out public images.

The tested working setup for building all images I've found is using a total of 3 VM:s. You might be able to cut it down with enough effort but there is a risk that you will run into filesystem issues if you for example try to use Fedora to build Rocky 9 images.

1. Rocky 9 - builds rocky9 and alma9.
2. Fedora 44 - builds fedora44.
3. Debian 13 - builds debian13 and ubuntu24.

If you don't want to publicly deploy your built image, you can change --public to --private in deploy.sh and add a project ID to it.

You can copy or symlink openstack-autobuild@.service and openstack-autobuild@.timer, and then do systemctl enable openstack-autobuild@$DISTRO.timer.