Function stringify

bolt/dwio/dwrf/test/ReaderTest.cpp:1316–1323

namespace {

std::vector<std::string> stringify(const std::vector<int32_t>& values) {
  std::vector<std::string> converted(values.size());
  std::transform(
      values.begin(), values.end(), converted.begin(), [](int32_t value) {
        return folly::to<std::string>(value);
      });
  return converted;
}

std::unordered_map<uint32_t, std::vector<std::string>> makeStructEncodingOption(
    const ColumnSelector& cs,