Enhance ArrayAgg to preserve input field nullability

### Is your feature request related to a problem or challenge?

`ArrayAgg` produces an output with data type:

```
DataType::List(Arc::new(Field::new_list_field(
arg_types[0].clone(),
true,
)))
```

If the input field is non-nullable, then we should be able to preserve this in the output.

### Describe the solution you'd like

Implement `return_field` and remove `return_type`. Preserve nullability of the input.

### Describe alternatives you've considered

_No response_

### Additional context

There are additional updates that will need to be made in the accumulator.