Update split_part to support negative indexes vs failing

[tshauck]

Is your feature request related to a problem or challenge?

No response

Describe the solution you'd like

I'd like split_part('a-b', '-', -1) to return b. Right now it returns an execution error. This is different postgres for example, which does work...

postgres=# SELECT split_part('a-b', '-', -1);
 split_part 
------------
 b
(1 row)

vs

DataFusion CLI v38.0.0
> SELECT split_part('a-b', '-', -1);
Execution error: field position must be greater than zero

Describe alternatives you've considered

No response

Additional context

No response