Support ManifestList in dockerregistry and importer

[soltysh]

Dockerhub serves ManifestList instead of regular Manifest if you provide it with information about having that type supported. Whenever we import github.com/docker/distribution/manifest/manifestlist which we do indirectly in integration tests we tell docherhub we do support this.

There was one attempt to bypass the problem temporarily: #16319 but that failed.

@dmage is currently working on a permanent fix

Make sure to revert:

• Disable TestImageStreamImportDockerHub integration test to unblock the queue #16324
• carry commit from image: set error when we receive unknown schema for the image #16319