feat: Remove dependency on deprecated hashicorp/template provider (#1297)

BREAKING CHANGES: We remove the dependency on the deprecated `hashicorp/template` provider and use the Terraform built in `templatefile` function. This will broke some workflows due to previously being able to pass in the raw contents of a template file for processing. The `templatefile` function requires a template file that exists before running a plan.

examples/managed_node_groups/versions.tf

@@ -5,7 +5,6 @@ terraform {
     aws        = ">= 3.22.0"
     local      = ">= 1.4"
     null       = ">= 2.1"
-    template   = ">= 2.1"
     random     = ">= 2.1"
     kubernetes = "~> 1.11"
   }