Podman Quadlet Support

At the moment, rexctl manages Podman entirely by itself, and does not group anything into a Pod. This may be irritating for users that already use Podman Quadlets to manage other rootless self hosted services with systemd in Pods.

A flag could be given to rexctl to dump container files into Podman's rootless unit search path, and group them into a Pod. Then, rexctl could ask systemd to start up the pod, which starts up all the containers.

Please see Podman's Quadlet docs:

• https://docs.podman.io/en/stable/markdown/podman-quadlet.1.html
• https://docs.podman.io/en/stable/markdown/podman-systemd.unit.5.html