test: Add JS CodeNode benchmark scenario (#10632)

packages/@n8n/benchmark/scenarios/jsCodeNodeOnceForEach/jsCodeNodeOnceForEach.script.js

@@ -0,0 +1,12 @@
+import http from 'k6/http';
+import { check } from 'k6';
+
+const apiBaseUrl = __ENV.API_BASE_URL;
+
+export default function () {
+	const res = http.post(`${apiBaseUrl}/webhook/code-node-benchmark`, {});
+	check(res, {
+		'is status 200': (r) => r.status === 200,
+		'has items in response': (r) => JSON.parse(r.body).length === 5,
+	});
+}