Implement gMock matchers to pretty print QuicErrorCode and QuicRstStreamErrorCode on failure.

Also change all relevant EXPECT_EQ and ASSERT_EQ expectations in three test
files to showcase new matcher.

Example output:

third_party/quic/core/quic_stream_test.cc:427: Failure
Value of: a
Expected: QUIC_NO_ERROR
Actual: 1 (of type quic::QuicErrorCode), QUIC_INTERNAL_ERROR

gfe-relnote: n/a, test-only change.
PiperOrigin-RevId: 277496262
Change-Id: I51a3e463b6261266609c7a7056d97a2ba9414fb5
diff --git a/quic/core/quic_stream_test.cc b/quic/core/quic_stream_test.cc
index d209454..0cee1fc 100644
--- a/quic/core/quic_stream_test.cc
+++ b/quic/core/quic_stream_test.cc
@@ -418,12 +418,12 @@
 
   QuicStreamPeer::CloseReadSide(stream_);
   stream_->CloseWriteSide();
-  EXPECT_EQ(QUIC_STREAM_NO_ERROR, stream_->stream_error());
-  EXPECT_EQ(QUIC_NO_ERROR, stream_->connection_error());
+  EXPECT_THAT(stream_->stream_error(), IsQuicStreamNoError());
+  EXPECT_THAT(stream_->connection_error(), IsQuicNoError());
   stream_->OnConnectionClosed(QUIC_INTERNAL_ERROR,
                               ConnectionCloseSource::FROM_SELF);
-  EXPECT_EQ(QUIC_STREAM_NO_ERROR, stream_->stream_error());
-  EXPECT_EQ(QUIC_NO_ERROR, stream_->connection_error());
+  EXPECT_THAT(stream_->stream_error(), IsQuicStreamNoError());
+  EXPECT_THAT(stream_->connection_error(), IsQuicNoError());
 }
 
 TEST_P(QuicStreamTest, RstAlwaysSentIfNoFinSent) {