test coreos next stream

[Luap99]

As pointed out by the coreos team we should test the next stream. This allows us to catch issues early and hopefully be able to react and fix them before they land in the stable stream. For releases we likely still want to use the stable stream.

My proposal would be to to make the main branch which is building the podman + 1 images (i.e. 5.4 right now) to base of the next stream. This image is used by podman's main branch during the development cycle for machine testing so we get plenty of testing there to catch issues.
And the actual release branches like (i.e. v5.3 right now) still base of stable. These images are used by actual end users that use stable podman releases. This way we ensure we do not break end users if something bad happens in the next stream.