AKS now provisions a StandardV2 NAT Gateway by default: zone-redundant, IPv6, no downgrade path

GA for new clusters using outboundType managedNATGateway with API version 2026-06-01 or later. StandardV2 needs StandardV2 public IPs, the Standard-to-StandardV2 upgrade is one-way, and the Service LoadBalancer still requires Standard IPs.