Request custom /path on registry maps including fallback

[prima101112]

Problem

we have a problem when using --registry-mirror its limited the default to just /library
could we just make this option out to the config
--mirror-prefix

we want to move the default docker hub with harbor proxy that actually go to dockerhub
but the harbor is not in the library instead on another prefix
correlated with issue
#1618 and #2471

and changes the

func normalizeReference(ref name.Reference, image string) (name.Reference, error) {
	if !strings.ContainsRune(image, '/') {
		return name.ParseReference("library/"+image, name.WeakValidation)
	}

	return ref, nil
}

https://github.com/GoogleContainerTools/kaniko/blob/main/pkg/image/remote/remote.go#L120

need feedback if its allowed we may pull request

[prima101112]

just adding PR also #3048

[JeromeJu]

Hi @prima101112 , thanks for filing this and the PR, please feel free to assign me for the rebased PR once it's ready.

[prima101112]

@JeromeJu already fix on this PR #3051 #3051

[JeromeJu]

Thanks will take a look

[prima101112]

PR already merged. thanks