cmd/k8s-operator: add replica support to nameserver (#17246)

This commit modifies the `DNSConfig` custom resource to allow specifying
a replica count when deploying a nameserver. This allows deploying
nameservers in a HA configuration.

Updates https://github.com/tailscale/corp/issues/32589

Signed-off-by: David Bond <davidsbond93@gmail.com>

k8s-operator/apis/v1alpha1/zz_generated.deepcopy.go

@@ -422,6 +422,11 @@ func (in *Nameserver) DeepCopyInto(out *Nameserver) {
 		*out = new(NameserverService)
 		**out = **in
 	}
+	if in.Replicas != nil {
+		in, out := &in.Replicas, &out.Replicas
+		*out = new(int32)
+		**out = **in
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new Nameserver.