Fix -Wdeprecated-declarations suppression on Windows

clang on Windows implements GNUC extensions, defines __clang__, but doesn't define __GNUC__, so one needs to handle both __clang__ and __GNUC__ cases. Fix this by using the existing PROTOBUF_IGNORE_DEPRECATION_* macros.

This upstreams (an improved version of) one of Chromium's patches: https://source.chromium.org/chromium/chromium/src/+/main:third_party/protobuf/patches/0049-deprecated-declarations-pragma.patch

PiperOrigin-RevId: 853514094

Author: protobuf-github-bot

src/google/protobuf/descriptor.cc

@@ -165,14 +165,9 @@ std::string ToJsonName(const absl::string_view input) {
 
 template <typename OptionsT>
 bool IsLegacyJsonFieldConflictEnabled(const OptionsT& options) {
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#endif
+  PROTOBUF_IGNORE_DEPRECATION_START
   return options.deprecated_legacy_json_field_conflicts();
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif
+  PROTOBUF_IGNORE_DEPRECATION_STOP
 }
 
 // Backport of fold expressions for the comma operator to C++11.