[data] [docs] Generalize fix for converting lists to np.ndarray in UDFs

[ericl]

Why are these changes needed?

The fix from https://github.com/ray-project/ray/pull/34734/files is at slightly the wrong point. Move it into the batch builder so that it also applies to other API sites such as map_groups.

[pcmoritz]

Should the list part also be removed in line 55 of python/ray/data/_internal/planner/map_batches.py (since it presumably already got converted?)

                    if not isinstance(value, (np.ndarray, list)):

I don't know this code super well so ^ might be wrong :)

[ericl]

Should the list part also be removed in line 55 of python/ray/data/_internal/planner/map_batches.py (since it presumably already got converted?)

This check is occurring earlier in the process, so we still need to be permissive on what types are allowed.