Fix [[maybe_unused]] anti-patterns in QUIC tests

Summary:
Replace `[[maybe_unused]] auto variable = method_call` patterns with proper assertions using `ASSERT_FALSE(method_call.hasError())` for quic::Expected return values. This improves test reliability by actually validating method call success instead of suppressing unused return value warnings.

## Changes Made

### 1. Fixed Anti-Patterns in Tests (84 instances across 5 test files):
- QuicTransportBaseTest.cpp: 74 patterns
- QuicTransportTest.cpp: 5 patterns
- QuicTypedTransportTest.cpp: 3 patterns
- QuicClientTransportLiteTest.cpp: 1 pattern
- QuicClientTransportTest.cpp: 1 pattern

For cleanup scenarios where failure is acceptable (e.g., setting read callback to nullptr), used `(void)method_call` instead of assertions to properly suppress warnings without incorrect success assertions.

### 2. Removed Unhelpful Comments (5 instances):
- QuicStreamAsyncTransport.cpp: Removed comments referencing "original behavior" that provided no actionable context

The logging statements (WARNING/VLOG) already make error handling behavior clear without need for historical commentary.

## Comprehensive Audit Results
Performed comprehensive audit of all `[[maybe_unused]]` usage in fbcode/quic/ (45 total instances):
- ✅ **Self-reference guards**: `[[maybe_unused]] auto self = sharedGuard();` - **LEGITIMATE**
- ✅ **Function parameter suppression**: Intentionally unused parameters - **LEGITIMATE**
- ✅ **Loop variable suppression**: Iteration without using values - **LEGITIMATE**
- ✅ **Static initialization**: Thread-local initialization patterns - **LEGITIMATE**
- ⛔ **Third-party code**: Left untouched as required
 ---
> Generated by [Confucius Code Assist (CCA)](https://www.internalfb.com/wiki/Confucius/Analect/Shared_Analects/Confucius_Code_Assist_(CCA)/)
[Session](https://www.internalfb.com/confucius?session_id=7be75dc0-61d5-11f0-8f26-27b21c240401&tab=Chat), [Trace](https://www.internalfb.com/confucius?session_id=7be75dc0-61d5-11f0-8f26-27b21c240401&tab=Trace)

Reviewed By: knekritz

Differential Revision: D78385516

fbshipit-source-id: 98c8989a147ed639be4582be3460b146aaa1075f

quic/api/test/QuicTransportTest.cpp

@@ -3438,8 +3438,7 @@ TEST_F(QuicTransportTest, FlowControlCallbacks) {
   // We should be able to create streams from this callback.
   EXPECT_CALL(connCallback_, onFlowControlUpdate(streamState2.value()->id))
       .WillOnce(Invoke([&](auto) {
-        [[maybe_unused]] auto newStream =
-            transport_->createBidirectionalStream();
+        ASSERT_FALSE(transport_->createBidirectionalStream().hasError());
       }));
   transport_->onNetworkData(
       SocketAddress("::1", 10000),
@@ -4069,9 +4068,11 @@ TEST_F(QuicTransportTest, InvokeTxCallbacksMultipleBytesWriteRateLimited) {
       .Times(1);
   auto transportRegisterTxCallback18 =
       transport_->registerTxCallback(stream, 0, &firstByteTxCb);
-  [[maybe_unused]] auto transportRegisterTxCallback19 =
-      transport_->registerTxCallback(
-          stream, kDefaultUDPSendPacketLen * 2, &secondPacketByteOffsetTxCb);
+  ASSERT_FALSE(
+      transport_
+          ->registerTxCallback(
+              stream, kDefaultUDPSendPacketLen * 2, &secondPacketByteOffsetTxCb)
+          .hasError());
   auto transportRegisterTxCallback20 =
       transport_->registerTxCallback(stream, lastByte, &lastByteTxCb);
   auto transportRegisterTxCallback21 =
@@ -5190,15 +5191,21 @@ TEST_F(QuicTransportTest, GetStreamPacketsTxedMultiplePackets) {
       .Times(1);
   auto transportRegisterTxCallback30 =
       transport_->registerTxCallback(stream, 0, &firstByteTxCb);
-  [[maybe_unused]] auto transportRegisterTxCallback32 =
-      transport_->registerTxCallback(
-          stream, firstPacketNearTailByte, &firstPacketNearTailByteTxCb);
-  [[maybe_unused]] auto transportRegisterTxCallback33 =
-      transport_->registerTxCallback(
-          stream, secondPacketNearHeadByte, &secondPacketNearHeadByteTxCb);
-  [[maybe_unused]] auto transportRegisterTxCallback34 =
-      transport_->registerTxCallback(
-          stream, secondPacketNearTailByte, &secondPacketNearTailByteTxCb);
+  ASSERT_FALSE(
+      transport_
+          ->registerTxCallback(
+              stream, firstPacketNearTailByte, &firstPacketNearTailByteTxCb)
+          .hasError());
+  ASSERT_FALSE(
+      transport_
+          ->registerTxCallback(
+              stream, secondPacketNearHeadByte, &secondPacketNearHeadByteTxCb)
+          .hasError());
+  ASSERT_FALSE(
+      transport_
+          ->registerTxCallback(
+              stream, secondPacketNearTailByte, &secondPacketNearTailByteTxCb)
+          .hasError());
   auto transportRegisterTxCallback31 =
       transport_->registerTxCallback(stream, lastByte, &lastByteTxCb);