Consider partial metadata requests for client reconciliation

New consumer implementing KIP-848 protocol needs to resolve metadata for the topics received in the assignment. It does so by relying on the centralized metadata object. Currently metadata updates requested through the metadata object, request metadata for all topics. Consider allowing the partial updates that are already expressed as an intention in the Metadata class but not fully supported (investigate background in case there were some specifics that led to this intention not being fully implemented)