Rewrote AWS Terraform for Kargo

Rewrote AWS Terraform deployment for AWS Kargo. It supports now
multiple Availability Zones, AWS Loadbalancer for Kubernetes API,
Bastion Host, ...

For more information see README

contrib/terraform/aws/modules/iam/variables.tf

@@ -0,0 +1,3 @@
+variable "aws_cluster_name" {
+    description = "Name of Cluster"
+}