message: json_data_handler: simplify big integer handling
diff: @@ -233,30 +233,13 @@ class json_data_handler : public cmdstan::json::json_handler {
  }
  void number_int64(int64_t n) {
  - set_last_dim();
  - // if integer overflow, promote numeric data to double
  - if (n > (int64_t)std::numeric_limits<int>::max()
  - || n < (int64_t)std::numeric_limits<int>::min())
  - promote_to_double();
  - if (is_int_) {
  - values_i_.push_back((int)n);
  - } else {
  - values_r_.push_back(n);
  - }
  - incr_dim_size();
  + // the number doesn't fit in int (otherwise number_int() would be called)
  + number_double(n);
  }
  void number_unsigned_int64(uint64_t n) {
  - set_last_dim();
  - // if integer overflow, promote numeric data to double
  - if (n > (uint64_t)std::numeric_limits<int>::max())
  - promote_to_double();
  - if (is_int_) {
  - values_i_.push_back((int)n);
  - } else {
  - values_r_.push_back(n);
  - }
  - incr_dim_size();
  + // the number doesn't fit in int (otherwise number_unsigned_int() would be called)
  + number_double(n);
  }
  void save_current_key_value_pair() {
  