[C++] Refactor util::Status

[Yannic]

This change refactors util::Status to have a similar shape as the
recently open-sourced absl::Status. This will allow Protobuf to
eventually use absl::Status and reduce the codesize.

Note that there is more work required before absl::Status can be used.

[acozzette]

What's the rationale for moving this to a new internal subdirectory?

[Yannic]

Just stylistic preference. We can keep the implementation in this file if you'd like, with or without namespace status_internal (although I'd prefer keeping the namespace to already give a hint that the symbols will come from a different namespace eventually)

[acozzette]

OK, I think it would be good to keep the code in the same files but moving them into a status_internal namespace sounds good.

[Yannic]

Alright, done!

[Yannic]

Thanks for running presubmit!

I tried looking at the logs but it seems like I don't have permissions.

[Yannic]

Just stylistic preference. We can keep the implementation in this file if you'd like, with or without namespace status_internal (although I'd prefer keeping the namespace to already give a hint that the symbols will come from a different namespace eventually)

[acozzette]

The CI run is showing an error like this:

src/google/protobuf/util/internal/json_stream_parser_test.cc:153:38: error: 'class google::protobuf::util::status_internal::Status' has no member named 'error_message'
     StringPiece error_message(result.error_message());
                                      ^

[Yannic]

The CI run is showing an error like this:

src/google/protobuf/util/internal/json_stream_parser_test.cc:153:38: error: 'class google::protobuf::util::status_internal::Status' has no member named 'error_message'
     StringPiece error_message(result.error_message());
                                      ^

Thanks! Looks like there was a second use of result.error_message() added there recently, rebased and fixed, PTAL

[acozzette]

Thanks @Yannic, it looks like there are a couple more call sites to fix in the conformance tests:

conformance_cpp.cc:137:54: error: no member named 'error_message' in 'google::protobuf::util::status_internal::Status'
                                  std::string(status.error_message()));
                                              ~~~~~~ ^
conformance_cpp.cc:192:32: error: no member named 'error_message' in 'google::protobuf::util::status_internal::Status'
            std::string(status.error_message()));

[Yannic]

Thanks @Yannic, it looks like there are a couple more call sites to fix in the conformance tests:

conformance_cpp.cc:137:54: error: no member named 'error_message' in 'google::protobuf::util::status_internal::Status'
                                  std::string(status.error_message()));
                                              ~~~~~~ ^
conformance_cpp.cc:192:32: error: no member named 'error_message' in 'google::protobuf::util::status_internal::Status'
            std::string(status.error_message()));

Thanks, fixed