Make request.method getter not allocate memory (#18961)

bench/snippets/request-method-getter.mjs

@@ -0,0 +1,14 @@
+import { bench, run } from "../runner.mjs";
+
+const url = "http://localhost:3000/";
+const clonable = new Request(url);
+
+bench("request.clone().method", () => {
+  return clonable.clone().method;
+});
+
+bench("new Request(url).method", () => {
+  return new Request(url).method;
+});
+
+await run();