Add UnknownArrayHandle::CastAndCallWithExtractedArray

The main point of this MR is to implement CastAndCallWithExtractedArray in UnknownArrayHandle. This provides a convenience for calling a function for most ArrayHandle types.

This was used to update some functions like MapFieldMergeAverage and MapFieldPermutation.

The extra use of RecombineVec defined by ArrayHandleRecombineVec required several fixes to make the behavior of the values more expected. For example, several assignment operators had to be added or fixed with RecombineVec and other Vec objects.