fmt9+ compatibility

[earies]

Summary:

Pass quic::LocalErrorCode to toString to return folly::StringPiece

/usr/include/fmt/core.h:2817:44:   required from ‘std::string fmt::v10::format(format_string<T ...>, T&& ...) [with T = {const char*, quic::LocalErrorCode, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >}; std::string = std::__cxx11::basic_string<char>; format_string<T ...> = basic_format_string<char, const char*, quic::LocalErrorCode, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >]’
/tmp/mvfst/quic/server/QuicServerWorker.cpp:697:27:   required from here
/usr/include/fmt/core.h:1691:7: error: static assertion failed: Cannot format an argument. To make type T formattable provide a formatter<T> specialization: https://fmt.dev/latest/api.html#udt
 1691 |       formattable,
      |       ^~~~~~~~~~~

[carlocab]

Already fixed in c96bd533d4264f7078fecc1b8f41b242d87830f9.

[jbeshay]

I will close this PR since this is covered by https://github.com/facebookincubator/mvfst/commit/c96bd533d4264f7078fecc1b8f41b242d87830f9