Store podman images to run on different machine.

[richtja]

Is your feature request related to a problem? Please describe.
Create mechanism for reproducing the same avocado run on different machine with podman spawner. Right now, the podman spawner will prepare a specific image for each test, and those images are reused when the same test is re-run. But this work only on the same machine. I would like that avocado will prepare thees images together with avocado configuration to be easily transportable between machines. Let's imagine that avocado will create an artifact for CI system, which anybody who has avocado and podman installed can download and run.