Use podman and skopeo for accessing containers, instead of Docker, remove dependency on /var/run/docker.sock

[rodrigc]

Is it possible to remove use of docker and /var/run/docker.sock from clairctl and
instead replace with https://github.com/containers/podman and https://github.com/containers/skopeo?

These tools are alternatives to the docker cli, and can build/push/pull containers from remote repositories
without depending on /var/run/docker.sock. podman's CLI is a drop-in replacement for the docker CLI, with
pretty much all the same command-line options supported.

I am trying to come up with a CI/CD pipeline which runs entirely within containers that calls clairctl.
clairctl seems to depend on /var/run/docker.sock, which doesn't work well when running clairctl inside a container.