refactor: Extract array_to_string and string_to_array from functions-array subcrate' s kernels and udf containers

[erenavsarogullari]

Which issue does this PR close?

Closes #9660.

What changes are included in this PR?

This PR aims to do following refactoring:
1- Extracts array_to_string and string_to_array functions from functions-array subcrate' s kernels and udf containers,
2- to_string and call_array_function macro_rules are being moved to string.rs,
3- downcast_arg macro_rule is being moved to util.rs,
4- make_scalar_function is applied to ArrayToString.invoke and StringToArray.invoke functions,
5- StringToArray.invoke function is refactored slightly,
Note: I preferred to submit this partial changeset for the review in order to avoid big-bang.

Are these changes tested?

Yes, all array.slt based array_to_string and string_to_array functions tests are passed.

Are there any user-facing changes?

No

[jayzhan211]

👍
Thanks @erenavsarogullari

[alamb]

Note: I preferred to submit this partial changeset for the review in order to avoid big-bang.

THank you 🙏