previously this mirrored one image at a time

the `Parse` function from library go prefers parsing ambiguous names as
repositories

for mirroring use-cases, we want to prefer parsing ambiguous names as
registries.

for example: `oc adm catalog mirror my-index:1 quay.io`

should parse `quay.io` as a registry name, not as
 `docker.io/library/quay.io`

the ambiguity can always be resolved by a user manually if needed by
fully qualifying a name they intended to be parsed as a repository

this ensures that the mirrored manifests can still reference the
manifestlist by digest

does not filter the mirrored images