Description of problem

If you set up a Gateway with a wildcard hostname the same as the wildcard app domain, and then delete that Gateway, you delete the wildcard record for the cluster.

Version-Release number of selected component (if applicable)

4.16

How reproducible

Every time.

Steps to Reproduce

1. Run the TestGatewayAPI e2e test to completion, or
2. Create a gatewayclass.
3. Create a gateway with hostname the same as the ingress controller apps domain (*.apps.xxx.yyy).
4. Delete the gateway.

Actual results

 When you delete the gateway it deletes the upstream DNS record for the ingress controller. Console, OAuth, and Canary routes will fail.

Expected results

No one should be allowed to create a gateway with the same hostname as the ingress controller apps domain.

Additional info

Two gateways can also claim the same host name. This might be an error in Istio (it probably ought to report Conflicted=True and Accepted=False). However, Istio accepts both gateways, and cluster-ingress-operator creates dnsrecords for both. The operator's dns controller needs to detect any scenario in which two dnsrecords have the same DNS name.