[FOLLOWUP] Investigate use of GpuScalar.getValue for MAP scalars in GpuRaiseError

[mythrocks]

This is a follow-up task for #11969.

GpuRaiseError currently uses GpuScalar.getValue to extract the value of errorParams from the GpuScalar argument in doColumnar(Int, GpuScalar, GpuScalar).

This might well be alright to do. All testing indicates that the Scalar has its host value set correctly.

However, if the host value isn't set, GpuScalar::getValue would use GpuScalar.extract to fetch the value. That method does not handle nested-type scalars correctly.

It would be worth investigating if that's a real possibility, and whether we should handle the map-scalar extraction differently.

[revans2]

Something similar likely shows up in other places too. It would be nice to just fix this for all nested types so we don't have to ever worry about it.