feat(publick8s, privatek8s) allow NAT gateways to AKS API

[dduportal]

Ref. jenkins-infra/helpdesk#3908

This PR adds the NAT gatewat public IP in the allow list for both publick8s and privatek8s to ensure all requests originated from inside the clusters (autoscaler, nodes healthchecks, API commands for kubectl logs/exec, etc.) are allowed to reach the control plane.

[dduportal]

Local run:

# azurerm_kubernetes_cluster.publick8s will be updated in-place
  ~ resource "azurerm_kubernetes_cluster" "publick8s" {
        # (29 unchanged attributes hidden)

      ~ api_server_access_profile {
          ~ authorized_ip_ranges     = [
              + "20.22.30.74/32",
              + "20.22.30.9/32",
              + "20.65.63.127/32",
              + "20.7.192.189/32",
              + "20.85.71.108/32",
                # (12 unchanged elements hidden)
            ]
            # (1 unchanged attribute hidden)
        }

        # (5 unchanged blocks hidden)
    }

Let's roll!