Adjust initialization in maximum and minimum (version 2) (#28116)
* Adjust initialization in maximum and minimum
Fixes #27836
* Reduce to first element in index range for OffsetArrays
* Adjust mapreduce to use first element in offset range as well.
Adjust tests
* Avoid defining global Areduc variable in reducedim tests
* Add comment in mapslices to explain the wrapping of scalars
* Change reduced_index for Slices and add test for previously failing
maximum of OffsetArray example
* Add checks that reductions along dimensions are inferred
