Add access traits CUDA example

Arndt, Danielrequested to merge
github/fork/dalg24/example_access_traits into master

Created by: dalg24

Demonstrating how one would specialize ArborX::Details::Traits::Access to construct a BVH without having to make a Kokkos::View of primitives.

Caught some small bugs along the way (call to Primitives::extent() and use of Primitives::execution_space). Might open a separate PR for these.

Will look into improving error messages in a later PR.

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