bug: array_length only return 1 element

[bubbajoe]

Describe the bug

select array_field from table

array_field
[abc, acb]
[bca, bac]
[cab, cba]

select array_length(array_field) from table

array_length(array_field)
2

To Reproduce

select array_length(array_field) from table

Expected behavior

select array_length(array_field) from table

array_length(array_field)
2
2
2

Additional context

array_field: Utf8

[Weijun-H]

I believe this problem arises from our approach of treating all instances of List as the same situation.
https://github.com/apache/arrow-datafusion/blob/94c442c8ff24a2b23f29d7579a0560c6daf76be9/datafusion/physical-expr/src/array_expressions.rs#L951-L958

[izveigor]

@bubbajoe the first implementation is only suitable for scalars. I will do for arrays soon.

[izveigor]

@bubbajoe Closed by #6864