Kubernetes 1.19 introduced v1 of the Ingress resource. The previous versions (extension/v1beta1 and networking/v1beta1) will be removed in Kubernetes 1.22. This is relatively short time. This PR adds support for v1 Ingress but keeps the networking/v1beta1 support present to keep it working on Kubernetes 1.16-1.18. The way it is designed makes it easy to remove the v1beta1 part in the future.

Kubernetes now also have new resource IngressClass which has the concept of default Ingress class. To make this work for the v1 Ingress in Strimzi, this also changes the default nginx class which was always set in the previous Strimzi versions.