Support creating multiple worker auto scaling groups, similar to KOPS

modules/worker_groups/data.tf

@@ -0,0 +1,9 @@
+data "aws_ami" "eks_worker" {
+  filter {
+    name   = "name"
+    values = ["eks-worker-*"]
+  }
+
+  most_recent = true
+  owners      = ["602401143452"] # Amazon
+}