[FIX] Move substitute files into a tmpl folder

Cleans up `envsubst` command and allows command to be re-run

tmpl/cluster-settings.yaml

@@ -0,0 +1,9 @@
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: cluster-settings
+  namespace: flux-system
+data:
+  METALLB_LB_RANGE: $BOOTSTRAP_METALLB_LB_RANGE
+  INGRESS_NGINX_LB: $BOOTSTRAP_INGRESS_NGINX_LB