Use TeamPolicy in Details::expandHalfToFull to improve performance

[dalg24]

In #809 we had opted to merge in the version with RangePolicy even though it was commented out with a macro guard in the code I was using to measure performance.
I don't have numbers handy to share but with the TeamPolicy version, findHalfNeighborList+expandHalfToFull is 15% faster than the "classic" BVH query implementation, with a RangePolicy it is slower than the current status quo.

[aprokop]

The patch itself looks fine. I think another minor improvement that should be done is doing
auto counts = KokkosExt::clone(space, offsets);
and then doing
indices(Kokkos::atomic_fetch_inc(&counts(i)) = <blah>;
inside the parallel_for.

This would

• avoid fetching offsets storage
• avoid doing index summation

[dalg24]

Current PR

|   |-> 6.61e-02 sec 8.1% 99.3% 0.0% 0.7% 1.06e+02 1 ArborX::Experimental::HalfToFull [region]
|   |   |-> 4.40e-02 sec 5.4% 100.0% 0.0% ------ 1 ArborX::Experimental::HalfToFull::rewrite [for]
|   |   |-> 2.15e-02 sec 2.6% 100.0% 0.0% ------ 1 ArborX::Experimental::HalfToFull::count [for]

VS your suggestion

|   |-> 6.53e-02 sec 8.0% 99.5% 0.0% 0.5% 1.07e+02 1 ArborX::Experimental::HalfToFull [region]
|   |   |-> 4.33e-02 sec 5.3% 100.0% 0.0% ------ 1 ArborX::Experimental::HalfToFull::rewrite [for]
|   |   |-> 2.15e-02 sec 2.6% 100.0% 0.0% ------ 1 ArborX::Experimental::HalfToFull::count [for]