Merge quic_test_impl into quiche_test_impl.

This is the only non-trivial move from quic/platform/impl to
quiche/common/platform/impl.  Every remaining impl file can simply be moved,
with an intermediate quiche/common/platform/api added.

PiperOrigin-RevId: 433224436

common/platform/api/quiche_test.h

diff --git a/common/platform/api/quiche_test.h b/common/platform/api/quiche_test.h
index efec638..a8b1e05 100644
--- a/common/platform/api/quiche_test.h
+++ b/common/platform/api/quiche_test.h
@@ -12,6 +12,15 @@
 template <class T>
 using QuicheTestWithParam = quiche::test::QuicheTestWithParamImpl<T>;
 
+using QuicheFlagSaver = QuicheFlagSaverImpl;
+
+// Class which needs to be instantiated in tests which use threads.
+using ScopedEnvironmentForThreads = ScopedEnvironmentForThreadsImpl;
+
+inline std::string QuicheGetTestMemoryCachePath() {
+  return QuicheGetTestMemoryCachePathImpl();
+}
+
 namespace quiche {
 namespace test {
 
@@ -27,4 +36,9 @@
 #define EXPECT_QUICHE_DEBUG_DEATH(condition, message) \
   EXPECT_QUICHE_DEBUG_DEATH_IMPL(condition, message)
 
+#define QUICHE_TEST_DISABLED_IN_CHROME(name) \
+  QUICHE_TEST_DISABLED_IN_CHROME_IMPL(name)
+
+#define QUICHE_SLOW_TEST(test) QUICHE_SLOW_TEST_IMPL(test)
+
 #endif  // QUICHE_COMMON_PLATFORM_API_QUICHE_TEST_H_