date_part declares a non-nullable result for non-null input, but can return NULL #26685

Describe the bug

date_part fails when a non-null input gives a NULL result:

SELECT extract(second from ts)
FROM (VALUES (arrow_cast(9223372036854775807, 'Timestamp(Second, None)'))) AS t(ts);
-- Arrow error: Invalid argument error: Column 'date_part(Utf8("SECOND"),t.ts)' is declared as non-nullable but contains null values

SELECT extract(hour from d)
FROM (VALUES (arrow_cast(9223372036854775807, 'Duration(Second)'))) AS t(d);
-- Arrow error: Invalid argument error: Column 'date_part(Utf8("HOUR"),t.d)' is declared as non-nullable but contains null values

To Reproduce

Run the queries above on main (dad9063be).

Expected behavior

Both return NULL.

Additional context

return_field_from_args takes the result's nullability from the input. Arrow's date_part returns NULL for some non-null inputs, such as timestamps it can't convert and values that overflow Int32 (Duration(s) hour).

The result was always nullable until #19823 (53.0.0). That PR added the Spark date_part, which simplifies to this function, and changed the nullability so the two fields would match (review thread). The Spark wrapper still takes its nullability from the inputs, so a fix here should change both to keep them matching. The optimizer's schema check (logically_equivalent_names_and_types) compares names and types but not nullability, so a mismatch between them would go unnoticed.

Part of #26672.

Willingness to contribute

I plan to contribute a fix for this bug independently.