[EventEngine] Add TODOs to re-enable EventEngine end2end tests (#33911)

These tests should be re-enabled before we claim confidence in the
engine implementations. It seems these tests are still being run, not
sure if that's true in all cases
([example](https://source.cloud.google.com/results/invocations/be524340-c98f-4915-a833-192047ae9925/targets/%2F%2Ftest%2Fcore%2Fend2end:call_creds_test@experiment%3Devent_engine_client/log)).

Alternatively, we can scrap this PR and enable all tests now if you feel
you're ready to start looking at PosixEventEngine test failures.

CC @yijiem @ctiller

test/core/end2end/tests/binary_metadata.cc

@@ -117,6 +117,7 @@ CORE_END2END_TEST(CoreEnd2endTest,
 
 CORE_END2END_TEST(CoreEnd2endTest,
                   BinaryMetadataServerHttp2FallbackClientHttp2Fallback) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   BinaryMetadata(*this, false, false);
 }

test/core/end2end/tests/call_creds.cc

@@ -288,6 +288,7 @@ CORE_END2END_TEST(PerCallCredsTest,
 
 CORE_END2END_TEST(PerCallCredsTest,
                   RequestResponseWithPayloadAndDeletedInsecureCallCreds) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   TestRequestResponseWithPayloadAndDeletedCallCreds(*this, false);
 }
@@ -304,6 +305,7 @@ CORE_END2END_TEST(PerCallCredsOnInsecureTest,
 
 CORE_END2END_TEST(PerCallCredsOnInsecureTest,
                   RequestResponseWithPayloadAndDeletedInsecureCallCreds) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   TestRequestResponseWithPayloadAndDeletedCallCreds(*this, false);
 }

test/core/end2end/tests/cancel_after_accept.cc

@@ -76,6 +76,7 @@ CORE_END2END_TEST(CoreDeadlineTest, DeadlineAfterAccept) {
 }
 
 CORE_END2END_TEST(CoreClientChannelTest, DeadlineAfterAcceptWithServiceConfig) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   InitServer(ChannelArgs());

test/core/end2end/tests/cancel_after_invoke.cc

@@ -104,21 +104,25 @@ void CancelAfterInvoke3(CoreEnd2endTest& test,
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, CancelAfterInvoke6) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   CancelAfterInvoke6(*this, std::make_unique<CancelCancellationMode>());
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, CancelAfterInvoke5) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   CancelAfterInvoke5(*this, std::make_unique<CancelCancellationMode>());
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, CancelAfterInvoke4) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   CancelAfterInvoke4(*this, std::make_unique<CancelCancellationMode>());
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, CancelAfterInvoke3) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   CancelAfterInvoke3(*this, std::make_unique<CancelCancellationMode>());
 }

test/core/end2end/tests/cancel_with_status.cc

@@ -81,6 +81,7 @@ CORE_END2END_TEST(CoreEnd2endTest, CancelWithStatus3) {
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, CancelWithStatus4) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   auto c = NewClientCall("/foo").Timeout(Duration::Seconds(5)).Create();
   CoreEnd2endTest::IncomingMetadata server_initial_metadata;

test/core/end2end/tests/filtered_metadata.cc

@@ -72,6 +72,7 @@ void TestRequestResponseWithMetadataToBeFiltered(
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, ContentLengthIsFiltered) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   TestRequestResponseWithMetadataToBeFiltered(*this, "content-length", "45");
 }

test/core/end2end/tests/retry_recv_initial_metadata.cc

@@ -35,6 +35,7 @@ namespace {
 // - first attempt receives initial metadata before trailing metadata,
 //   so no retry is done even though status was ABORTED
 CORE_END2END_TEST(RetryTest, RetryRecvInitialMetadata) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_CLIENT();
   InitServer(ChannelArgs());
   InitClient(ChannelArgs().Set(

test/core/end2end/tests/simple_request.cc

@@ -99,6 +99,7 @@ void SimpleRequestBody(CoreEnd2endTest& test) {
 }
 
 CORE_END2END_TEST(CoreEnd2endTest, SimpleRequest) {
+  // TODO(vigneshbabu): re-enable these before release
   SKIP_IF_USES_EVENT_ENGINE_LISTENER();
   SimpleRequestBody(*this);
 }