Support for EKS Managed Node Groups (#602)

* Finished first cut of managed node groups

* Updated formatting and extra fields.

* Updating Changelog and README

* Fixing formatting

* Fixing docs.

* Updating required Version

* Updating changelog

* Adding example for managed node groups

* Managed IAM Roles for Nodegroups now have correct policies. Tags can now be added to node groups.

* Fixing bug where people could set source_security_group_ids without setting ssh key causing a race condition within the aws provider.

* Adding lifecycle create_before_destroy

* Adding random pet names for create_before_destroy

* Updating per comments.

* Updating required versions of terraform

* Updating per comments.

* Updating vars

* Updating minimum version for terraform

* Change worker_groups_managed_node_groups to node_groups

* Using for_each on the random_pet

* Adding changes recommended by @eytanhanig

* Update node_groups.tf

examples/managed_node_groups/variables.tf

@@ -0,0 +1,52 @@
+variable "region" {
+  default = "us-west-2"
+}
+
+variable "map_accounts" {
+  description = "Additional AWS account numbers to add to the aws-auth configmap."
+  type        = list(string)
+
+  default = [
+    "777777777777",
+    "888888888888",
+  ]
+}
+
+variable "map_roles" {
+  description = "Additional IAM roles to add to the aws-auth configmap."
+  type = list(object({
+    rolearn  = string
+    username = string
+    groups   = list(string)
+  }))
+
+  default = [
+    {
+      rolearn  = "arn:aws:iam::66666666666:role/role1"
+      username = "role1"
+      groups   = ["system:masters"]
+    },
+  ]
+}
+
+variable "map_users" {
+  description = "Additional IAM users to add to the aws-auth configmap."
+  type = list(object({
+    userarn  = string
+    username = string
+    groups   = list(string)
+  }))
+
+  default = [
+    {
+      userarn  = "arn:aws:iam::66666666666:user/user1"
+      username = "user1"
+      groups   = ["system:masters"]
+    },
+    {
+      userarn  = "arn:aws:iam::66666666666:user/user2"
+      username = "user2"
+      groups   = ["system:masters"]
+    },
+  ]
+}