feat: Replace the local-exec script with a http datasource for waiting cluster (#1339)

NOTES: Using the [terraform-aws-modules/http](https://registry.terraform.io/providers/terraform-aws-modules/http/latest) provider is a more platform agnostic way to wait for the cluster availability than using a local-exec. With this change we're able to provision EKS clusters and manage the `aws_auth` configmap while still using the `hashicorp/tfc-agent` docker image.

versions.tf

@@ -4,9 +4,12 @@ terraform {
   required_providers {
     aws        = ">= 3.37.0"
     local      = ">= 1.4"
-    null       = ">= 2.1"
     template   = ">= 2.1"
     random     = ">= 2.1"
     kubernetes = ">= 1.11.1"
+    http = {
+      source  = "terraform-aws-modules/http"
+      version = ">= 2.2.0"
+    }
   }
 }