message: Report correct buffer size in buffered mode.
diff: @@ -1521,7 +1521,9 @@ Http::FilterDataStatus Context::decodeData(::Envoy::Buffer::Instance& data, bool
  }
  request_body_buffer_ = &data;
  end_of_stream_ = end_stream;
  - auto result = convertFilterDataStatus(onRequestBody(data.length(), end_stream));
  + const auto buffer = getBuffer(WasmBufferType::HttpRequestBody);
  + const auto buffer_size = (buffer == nullptr) ? 0 : buffer->size();
  + auto result = convertFilterDataStatus(onRequestBody(buffer_size, end_stream));
  buffering_request_body_ = false;
  switch (result) {
  case Http::FilterDataStatus::Continue:
  @@ -1589,7 +1591,9 @@ Http::FilterDataStatus Context::encodeData(::Envoy::Buffer::Instance& data, bool
  }
  response_body_buffer_ = &data;
  end_of_stream_ = end_stream;
  - auto result = convertFilterDataStatus(onResponseBody(data.length(), end_stream));
  + const auto buffer = getBuffer(WasmBufferType::HttpResponseBody);
  + const auto buffer_size = (buffer == nullptr) ? 0 : buffer->size();
  + auto result = convertFilterDataStatus(onResponseBody(buffer_size, end_stream));
  buffering_response_body_ = false;
  switch (result) {
  case Http::FilterDataStatus::Continue:
  