message: use QUIC cc string to type conversion func
diff: #include <folly/portability/GFlags.h>
  #include <folly/stats/Histogram.h>
  +#include <quic/QuicConstants.h>
  #include <quic/client/QuicClientTransport.h>
  #include <quic/common/test/TestUtils.h>
  #include <quic/congestion_control/ServerCongestionControllerFactory.h>
  @@ -691,22 +692,13 @@ class TPerfClient : public quic::QuicSocket::ConnectionCallback,
  using namespace quic::tperf;
  quic::CongestionControlType flagsToCongestionControlType(
  - const std::string& congestionControlType) {
  - if (congestionControlType == "cubic") {
  - return quic::CongestionControlType::Cubic;
  - } else if (congestionControlType == "newreno") {
  - return quic::CongestionControlType::NewReno;
  - } else if (congestionControlType == "bbr") {
  - return quic::CongestionControlType::BBR;
  - } else if (congestionControlType == "copa") {
  - return quic::CongestionControlType::Copa;
  - } else if (congestionControlType == "ccp") {
  - return quic::CongestionControlType::CCP;
  - } else if (congestionControlType == "none") {
  - return quic::CongestionControlType::None;
  - }
  + const std::string& congestionControlFlag) {
  + auto ccType = quic::congestionControlStrToType(congestionControlFlag);
  + if (!ccType) {
  throw std::invalid_argument(folly::to<std::string>(
  - "Unknown congestion controller ", congestionControlType));
  + "Unknown congestion controller ", congestionControlFlag));
  + }
  + return *ccType;
  }
  int main(int argc, char* argv[]) {
  