Migrate cluster modules from map(map(string)) to map(object)

 * refactor code to not rely on _modules anymore removing
   one level of module nesting for easier maintainability
 * provide move blocks for all affected modules and
   resources
 * introduce mandatory cluster output on cluster modules
   and corresponding input on node pool modulesto reduce
   dependence on data sources causing issues when using
   the node pool module for the clsuter provisioned default
   node pool
 * unify node pool module inputs between providers using
   new cluster module output
 * reduce use of locals to improve DX for contributions and
   maintenance work
 * added support for merging of nested maps and objects to
   inheritance module and updated previous string vars to
   more specific types

Author: pst

.github/workflows/main.yml

@@ -173,7 +173,7 @@ jobs:
         sed -i 's/region = ""/region = "eu-west-1"/g' eks_zero_providers.tf || true
 
         # EKS: set cluster_availability_zones
-        sed -i 's/cluster_availability_zones = ""/cluster_availability_zones = "eu-west-1a,eu-west-1b"/g' eks_zero_cluster.tf || true
+        sed -i 's/cluster_availability_zones = \[\]/cluster_availability_zones = ["eu-west-1a", "eu-west-1b"]/g' eks_zero_cluster.tf || true
 
         # GKE: set project_id
         sed -i 's/project_id = ""/project_id = "terraform-kubestack-testing"/g' gke_zero_cluster.tf || true
@@ -182,7 +182,7 @@ jobs:
         sed -i 's/region = ""/region = "europe-west1"/g' gke_zero_cluster.tf || true
 
         # GKE: set cluster_node_locations
-        sed -i 's/cluster_node_locations = ""/cluster_node_locations = "europe-west1-b,europe-west1-c,europe-west1-d"/g' gke_zero_cluster.tf || true
+        sed -i 's/cluster_node_locations = \[\]/cluster_node_locations = ["europe-west1-b", "europe-west1-c", "europe-west1-d"]/g' gke_zero_cluster.tf || true
 
     - name: "Terraform init"
       working-directory: ./kubestack-starter-${{ matrix.starter }}