Move configuration of servers completely to ansible

With this change we no longer use user-data scripts on the provided
machines. That makes it way easier for me to handle all the
configuration, since I only have to run ansible. Furthermore this the
burdon to think what may went wrong, since ansible is easier to debug
than some arbitrary scripts which run at provisioning-time on the
machines.

With this change I should also think about restructuring the code a bit
as well. Since it's actually easier to provide the initial
software-stack for the cluster via ansible than via terraform, at least
as far as I can tell right now.

infra/main.tf

@@ -59,8 +59,10 @@ module "k8s" {
 resource "local_file" "ansible_inventory" {
   filename = "${path.module}/../k3s/inventory.ini"
   content = templatefile("./inventory.ini.tftpl", {
-    server_ips  = module.k8s.server_ips_v4,
-    agent_ips   = module.k8s.agent_ips_v4,
+    server_ips   = module.k8s.server_ips_v4,
+    agent_ips    = module.k8s.agent_ips_v4,
+    network_cidr = module.k8s.private_network_cidr,
+    private_nat  = module.k8s.private_network_nat,
   })
 }