feat: Drop random pets from Managed Node Groups (#1372)

BREAKING CHANGES: We now decided to remove `random_pet` resources in Managed Node Groups (MNG). Those were used to recreate MNG if something change and also simulate the newly added argument `node_group_name_prefix`. But they were causing a lot of troubles. To upgrade the module without recreating your MNG, you will need to explicitly reuse their previous name and set them in your MNG `name` argument. Please see [upgrade docs](https://github.com/terraform-aws-modules/terraform-aws-eks/blob/master/docs/upgrades.md#upgrade-module-to-v1700-for-managed-node-groups) for more details.

modules/node_groups/node_groups.tf

@@ -1,7 +1,8 @@
 resource "aws_eks_node_group" "workers" {
   for_each = local.node_groups_expanded
 
-  node_group_name = lookup(each.value, "name", join("-", [var.cluster_name, each.key, random_pet.node_groups[each.key].id]))
+  node_group_name_prefix = lookup(each.value, "name", null) == null ? local.node_groups_names[each.key] : null
+  node_group_name        = lookup(each.value, "name", null)
 
   cluster_name  = var.cluster_name
   node_role_arn = each.value["iam_role_arn"]