support array with scalar arithmetic operation for decimal data type

[liukun4515]

Which issue does this PR close?

part of #122

schema:
CREATE EXTERNAL TABLE food (a DECIMAL(10,5), b decimal(20,15), c boolean) xxxx;

This query select a+b from table was supported, but the query select a+10 from table is not supported.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[alamb]

Looks good @liukun4515

[alamb]

It would be great to move some / all of this decimal manipulation into the arrow-rs crate at some point

[liukun4515]

thanks for your reminder and I have a plan to do this.

[liukun4515]

But now I find a bug in the arithmetic operation. https://github.com/apache/arrow-datafusion/blob/c91efc27658e58264c4f346a5cfdec8810179e90/datafusion/physical-expr/src/expressions/binary.rs#L302 and https://github.com/apache/arrow-datafusion/blob/c91efc27658e58264c4f346a5cfdec8810179e90/datafusion/physical-expr/src/expressions/binary.rs#L307

In the divide method, we may lose of precision by converting the i128 to f64.
We use the f64 to store the larger range of data, but we lose the precision.

I will try to figure out this issue and resolve this.

[liukun4515]

I think It can be merged

[alamb]

I think It can be merged

Sounds good to me -- feel free to do it yourself next time; I normally wait for at least one approving review from a maintainer or active contributor. If the change is trivial I'll merge it then and if a little more involved I try and leave it open for 24 hours.

[alamb]

Thanks again @liukun4515