Function round support two format round(double) and round(double, int), the argument is variadic.
But FunctionBinaryArithmetic not support variadic argument now, make get_function for round(double, int) failed.
reproduce steps:
1. set enable_vectorized_engine=true;
2. try to call round(double, int);
```
> select round(10.12345,2);
ERROR 1105 (HY000): errCode = 2, detailMessage = Function round is not implemented
```
