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_session_test.cc b/quic/core/quic_session_test.cc
index e13f0db..b07a232 100644
--- a/quic/core/quic_session_test.cc
+++ b/quic/core/quic_session_test.cc
@@ -85,7 +85,7 @@
       error =
           session()->config()->ProcessPeerHello(msg, CLIENT, &error_details);
     }
-    EXPECT_EQ(QUIC_NO_ERROR, error);
+    EXPECT_THAT(error, IsQuicNoError());
     session()->OnConfigNegotiated();
     session()->connection()->SetDefaultEncryptionLevel(
         ENCRYPTION_FORWARD_SECURE);