Zone appears as both public and private

Issue descriptionIssue description

When you create a Cloud DNS zone, it appears as both public and private.

SolutionSolution

The Terraform provider creates a public-private zone so you can make it accessible from private networks without recreating it. As long as the private_visibility.network_ids list is empty, such a zone behaves like a regular public zone.

This is to make sure that most of the zones can be updated without recreation.