This commit tweaks the excellent work from Gianluca in PR#1550 a
little bit. Now that the container inputs are their own input
type some of the code that used to be part of the original
`inputs/org.osbuild.containers` can be simplified.
An input that pairs with the org.osbuild.containers-storage source. It
makes the host container storage available to a stage and a container ID
for the stage to use.
Unlike all the other input types, this input does not refer to static
objects in the osbuild sources store but a dynamically mounted container
store that depends on the host storage configuration and the
availability of specific containers in that store.
Co-authored-by: Achilleas Koutsou <achilleas@koutsou.net>
Co-authored-by: Gianluca Zuccarelli <gzuccare@redhat.com>
