Users want to get rounding mode in `quantileExact` equivalent to "median_low" from Python:
https://docs.python.org/3/library/statistics.html#statistics.median_low
while current implementation works equivalent to "median_high" (?)
/** Generic aggregate function for calculation of quantiles.
  * It depends on quantile calculation data structure. Look at Quantile*.h for various implementations.
  */
template <
    
    typename Value,
    
    typename Data,
    
    typename Name,
    
    
    
    bool has_second_arg,
    
    
    
    typename FloatReturnType,
    
    
    bool returns_many
>
class AggregateFunctionQuantile final : public IAggregateFunctionDataHelper<Data,