UpCloud server plan, firewall, load balancer integration (#8758)

* [upcloud] add option to use preconfigured cpu/mem plan

* [upcloud] add option to use firewall rules for API server/SSH access

* [upcloud] add option to use managed load balancer

contrib/terraform/upcloud/modules/kubernetes-cluster/output.tf

@@ -18,3 +18,7 @@ output "worker_ip" {
     }
   }
 }
+
+output "loadbalancer_domain" {
+  value = var.loadbalancer_enabled ? upcloud_loadbalancer.lb[0].dns_name : null
+}