Implement `fill` and `set` methods for `ArrayView`

[gunney1]

It would be nice to have fill and set methods for ArrayView, similar to those for Array, so we can use it for memory not belonging to Array.

@kennyweiss said in a Teams chat:

Seems like we should also add axom::ArrayView::fill() since those apply to an external buffer/array and do not involve memory allocation/reallocations. It should have the same API as axom::Array::fill()

We should probably also have axom::ArrayView::set()

We might want to add an axom::fill to our memory_management functions (akin to axom::copy() and axom::allocate())

[BradWhitlock]

I added ArrayView::fill() in an earlier PR so I'll finish this one.