improve performance for round(col_floating, frac)

[guo-shaoge]

Enhancement

For now, TiDBFloatingRound use std::pow to compute base, which may hurt performance. Should use pre-computed array, like TiDBDecimalRound and TiDBIntegerRound, check

tiflash/dbms/src/Functions/FunctionsRound.h

Line 1032 in 0001db3

using Pow = ConstPowOf10<UnsignedOutput, digits>;