refactor(service-worker): set http method in MockRequest constructor (#33930)

Enable to create mocks for mutating http requests in tests
to check more scenarios.

PR Close #33930

packages/service-worker/worker/testing/fetch.ts

@@ -110,6 +110,9 @@ export class MockRequest extends MockBody implements Request {
     if (init.credentials !== undefined) {
       this.credentials = init.credentials;
     }
+    if (init.method !== undefined) {
+      this.method = init.method;
+    }
   }
 
   clone(): Request {