Use QuicheTest and quiche_test.h in third_party/http2.

The motivation is that these files have to be included with
#pragma clang diagnostic ignored "-Weverything", otherwise CLs touching test
files will not build.

PiperOrigin-RevId: 334632337
Change-Id: I74d8cdef4b07eed79880d1ca7e0476b3a2c5c184
diff --git a/http2/hpack/varint/hpack_varint_encoder_test.cc b/http2/hpack/varint/hpack_varint_encoder_test.cc
index 22de704..dcbff8a 100644
--- a/http2/hpack/varint/hpack_varint_encoder_test.cc
+++ b/http2/hpack/varint/hpack_varint_encoder_test.cc
@@ -7,7 +7,7 @@
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_utils.h"
 #include "net/third_party/quiche/src/common/platform/api/quiche_arraysize.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "net/third_party/quiche/src/common/platform/api/quiche_test.h"
 
 namespace http2 {
 namespace test {