Expose registry CAs as one to MCO

To enable the MCO to replace the node-ca, the registry operator needs to provide its own CAs in isolation.

Currently, the registry provides its own CAs via the "image-registry-certificates" configmap. This configmap is a merge of the service ca, storage ca, and additionalTrustedCA (from images.config.openshift.io/cluster).

Because the MCO already has access to additionalTrustedCA, the new secret does not need to contain it.

ACCEPTANCE CRITERIA

TBD