Add a new platform API QuicheScopedDisableExitOnDFatal to allow Envoy's QUIC code switching to use platform API implementation under net/quic/platform_overrides/.

This is needed because third_party/envoy/src/test/common/http/codec_impl_fuzz_test.cc uses setDFatalExitDisabled() which is defined in third_party/envoy/src/source/common/quic/platform/quiche_logging_impl.h. As we are switching away from third_party/envoy/src/source/common/quic/platform/, we need to use a similar internal utility ScopedDisableExitOnDFatal to replace it.

PiperOrigin-RevId: 599839490

quiche/common/platform/api/quiche_test.h

diff --git a/quiche/common/platform/api/quiche_test.h b/quiche/common/platform/api/quiche_test.h
index a1e3cff..e013ba6 100644
--- a/quiche/common/platform/api/quiche_test.h
+++ b/quiche/common/platform/api/quiche_test.h
@@ -16,6 +16,8 @@
 
 using QuicheFlagSaver = QuicheFlagSaverImpl;
 
+using QuicheScopedDisableExitOnDFatal = QuicheScopedDisableExitOnDFatalImpl;
+
 // Class which needs to be instantiated in tests which use threads.
 using ScopedEnvironmentForThreads = ScopedEnvironmentForThreadsImpl;