GH-41011: [C++] Add an output type resolver for decimal types in CompareFunction so can be casted correctly

[ZhangHuiGui]

Rationale for this change

Fix the problem that decimal types array compare with different scales make error results.

What changes are included in this PR?

Add an output type resolver for decimal types in CompareFunction so can be casted correctly

Are these changes tested?

Yes

Are there any user-facing changes?

Yes, decimal type's comparison operations with different scale will be correct.

Co-authored-by ZhangHuiGui [email protected] Co-authored-by laotan332 [email protected]

• GitHub Issue: #41011