This PR adds the quantileExactLow and quantileExactHigh
implementations which are equivalent to how the `median_low`
and `median_high` functions are implemented in python.

`median_low`: https://github.com/python/cpython/blob/master/Lib/statistics.py#L438
`median_high`: https://github.com/python/cpython/blob/master/Lib/statistics.py#L460

This reverts commit 1e261654.

* Fix lgamma race.

There is no need to capture query AST for the status_info_to_query_log,
since callers already captured it anyway.

gcc10 reports:
    ../src/Interpreters/executeQuery.cpp: In member function ‘void std::__1::function<_Rp(_ArgTypes ...)>::swap(std::__1::function<_Rp(_ArgTypes ...)>&) [with _Rp = void; _ArgTypes = {DB::IBlockInputStream*, DB::IBlockOutputStream*, DB::QueryPipeline*}]’:
    ../src/Interpreters/executeQuery.cpp:490:49: error: array subscript 35 is outside array bounds of ‘std::__1::aligned_storage<32, 16>::type [1]’ [-Werror=array-bounds]
      490 |             auto status_info_to_query_log = [ast](QueryLogElement &element, const QueryStatusInfo &info) mutable
          |                                                 ^
    In file included from ../contrib/libcxx/include/algorithm:644,
                     from ../contrib/libcxx/include/__string:57,
                     from ../contrib/libcxx/include/string_view:175,
                     from ../contrib/libcxx/include/string:504,
                     from ../src/Common/formatReadable.h:3,                                                                                                  from ../src/Interpreters/executeQuery.cpp:1:
    ../contrib/libcxx/include/functional:1877:60: note: while referencing ‘__tempbuf’
     1877 |             typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
          |                                                            ^~~~~~~~~