Upcloud: Add possibility to setup cluster using nodes with no public IPs (#11696)

* terraform upcloud: Added possibility to set up nodes with only private IPs

* terraform upcloud: add support for gateway in private zone

* terraform upcloud: split LB proxy protocol config per backend

* terraform upcloud: fix flexible plans

* terraform upcloud: Removed overview of cluster setup

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Co-authored-by: davidumea <david.andersson@elastisys.com>

contrib/terraform/upcloud/output.tf

@@ -7,6 +7,10 @@ output "worker_ip" {
   value = module.kubernetes.worker_ip
 }
 
+output "bastion_ip" {
+  value = module.kubernetes.bastion_ip
+}
+
 output "loadbalancer_domain" {
   value = module.kubernetes.loadbalancer_domain
 }