Add Flow.getSetting for resolving env-var properties

This lays the groundwork for subflow-specific settings

packages/node_modules/@node-red/runtime/lib/nodes/flows/Flow.js

@@ -283,6 +283,10 @@ class Flow {
         return this.activeNodes;
     }
 
+    getSetting(key) {
+        return this.parent.getSetting(key);
+    }
+
     handleStatus(node,statusMessage) {
         events.emit("node-status",{
             id: node.id,