Delete DartIsolateTest.PlatformIsolateSendAndReceive (#55722)

This test is flaky on the mac bots, but I can't repro the failure locally. Sending and receiving messages from the platform isolate is covered more realistically by the [Dart test](https://github.com/flutter/engine/blob/fd1ccdb95e0380d461812c9a6cd2684861970cb9/testing/dart/platform_isolate_test.dart#L65), so this test isn't very useful anyway.

Closes flutter/flutter#156251

Author: liamappelbe

runtime/dart_isolate_unittests.cc

@@ -892,79 +892,6 @@ TEST_F(DartIsolateTest, PlatformIsolateEarlyShutdown) {
   // root isolate will be auto-shutdown
 }
 
-TEST_F(DartIsolateTest, PlatformIsolateSendAndReceive) {
-  fml::AutoResetWaitableEvent message_latch;
-  AddNativeCallback(
-      "PassMessage",
-      CREATE_NATIVE_ENTRY(([&message_latch](Dart_NativeArguments args) {
-        auto message = tonic::DartConverter<std::string>::FromDart(
-            Dart_GetNativeArgument(args, 0));
-        ASSERT_EQ("Platform isolate received: Hello from root isolate!",
-                  message);
-        message_latch.Signal();
-      })));
-
-  FakePlatformConfigurationClient client;
-  auto platform_configuration =
-      std::make_unique<PlatformConfiguration>(&client);
-
-  ASSERT_FALSE(DartVMRef::IsInstanceRunning());
-  auto settings = CreateSettingsForFixture();
-  auto vm_ref = DartVMRef::Create(settings);
-  ASSERT_TRUE(vm_ref);
-  auto vm_data = vm_ref.GetVMData();
-  ASSERT_TRUE(vm_data);
-
-  auto platform_thread = CreateNewThread();
-  auto ui_thread = CreateNewThread();
-  TaskRunners task_runners(GetCurrentTestName(),  // label
-                           platform_thread,       // platform
-                           ui_thread,             // raster
-                           ui_thread,             // ui
-                           ui_thread              // io
-  );
-  auto isolate = RunDartCodeInIsolate(
-      vm_ref, settings, task_runners, "emptyMain", {},
-      GetDefaultKernelFilePath(), {}, std::move(platform_configuration));
-  ASSERT_TRUE(isolate);
-  auto root_isolate = isolate->get();
-  ASSERT_EQ(root_isolate->GetPhase(), DartIsolate::Phase::Running);
-
-  fml::AutoResetWaitableEvent ui_thread_latch;
-  Dart_Isolate platform_isolate = nullptr;
-  fml::TaskRunner::RunNowOrPostTask(
-      ui_thread, fml::MakeCopyable([&]() mutable {
-        ASSERT_TRUE(isolate->RunInIsolateScope([root_isolate,
-                                                &platform_isolate]() {
-          Dart_Handle lib = Dart_RootLibrary();
-          Dart_Handle entry_point = Dart_Invoke(
-              lib, tonic::ToDart("createEntryPointForPlatIsoSendAndRecvTest"),
-              0, nullptr);
-          char* error = nullptr;
-          platform_isolate =
-              root_isolate->CreatePlatformIsolate(entry_point, &error);
-          EXPECT_FALSE(error);
-          return true;
-        }));
-        ui_thread_latch.Signal();
-      }));
-  ui_thread_latch.Wait();
-
-  // Wait for a message from the platform isolate.
-  message_latch.Wait();
-
-  // Post a task to the platform_thread that runs after the platform isolate's
-  // entry point and all messages, and wait for it to run.
-  fml::AutoResetWaitableEvent epilogue_latch;
-  fml::TaskRunner::RunNowOrPostTask(
-      platform_thread, fml::MakeCopyable([&epilogue_latch]() mutable {
-        epilogue_latch.Signal();
-      }));
-  epilogue_latch.Wait();
-
-  // root isolate will be auto-shutdown
-}
-
 TEST_F(DartIsolateTest, PlatformIsolateCreationAfterManagerShutdown) {
   AddNativeCallback("PassMessage",
                     CREATE_NATIVE_ENTRY((