fix: derive custom nullable for spark make_interval

[kumarUjjawal]

Which issue does this PR close?

• Closes #19155.
• Part of #19144

Rationale for this change

What changes are included in this PR?

• Spark make_interval use the return_field_from_args for handling nullability better
• Unit tests to confirm this change

Are these changes tested?

• Added new unit tests, the previous tests pass

Are there any user-facing changes?

[kumarUjjawal]

Right. I’ll update return_field_from_args to always mark the result nullable (matching Spark’s nullable behavior), and adjust the nullability test accordingly.

[kumarUjjawal]

@martin-g If we change the return-field policy to “always nullable” , the old comments about zero-arg/non-nullable outputs becomes incorrect, should I change that too?

[martin-g]

Good point! Then it should be non-nullable for zero-arg and nullable for the other cases.