oc adm release - add heterogeneous architecture support

tl;dr

oc adm release new (and related verbs info, extract, mirror) would be enhanced to optionally allow the creation of manifest list release payloads. The manifest list flow would be triggered whenever the CVO image in an imagestream was a manifest list. If the CVO image is a standard manifest, the generated release payload will also be a manifest. If the CVO image is a manifest list, the generated release payload would be a manifest list (containing a manifest for each arch possessed by the CVO manifest list).

In either case, oc adm release new would permit non-CVO component images to be manifest or manifest lists and pass them through directly to the resultant release manifest(s).

If a manifest list release payload is generated, each architecture specific release payload manifest will reference the same pullspecs provided in the input imagestream.

More details in Option 1 of https://docs.google.com/document/d/1BOlPrmPhuGboZbLZWApXszxuJ1eish92NlOeb03XEdE/edit#heading=h.eldc1ppinjjh