[ci] Use podman for building

- Building with nvidia-container-runtime results in host GPU driver libraries saved in the built image,
  which causes runtime failures when trying to run CUDA programs after host GPU drivers are updated.
- The docker daemon must be set to use nvidia-container-runtime by default, because neither docker-compose
  nor jupyterhub allow choosing a container runtime other than the default one.
- docker buildkit, which would be an alternative, fails to even start building