We use axes in many downstream computations that may not re-index directly into the original array, so we add a second type parameter to `Slice` that is turned on when converting `:` in indexing expressions -- and really only `SubArray` cares about.

…ty edge-cases

Alleviates #28928 but does not completely remove allocations due to the allocation of the view that gets passed to `map!`.

that we will encourage offset array implementations to use instead of Base.Slice