Organize call responsibilities for expr.Eval

[k2tzumi]

The logic to evaluate an expression against a store is duplicated in several programs.

We are dealing directly with the antonmedv/expr library, which we believe is problematic for unified expression expansion.

I think we need to organize the use cases for the process of evaluating expressions, clarify who is in charge of the logic, and do some refactoring.

[k1LoW]

Hi @k2tzumi

We have integrated the functions related to the expr package in eval.go

I think this has achieved a certain level of success, but what do you think?

[k2tzumi]

@k1LoW

Yes. I think we have been able to integrate.
Thank you for your response!