Enable alternate projection onto space filling curve

[dalg24]

Per discussion on #637 enable using 32-bit Morton codes

[aprokop]

I am mostly OK with things in ArborX_DetailsTreeConstruction.hpp. But in the BVH interface, I'd rather use enums, unless you want to allow users to provide their own curves (and in that case, I'm not sure what the right operator() interface is).

Have some issues with names, but that can be ironed out later.

[aprokop]

You accidentally introduced a subtlety here that one need to remember about. It is still correct, but now also depends on the fact that i ^ (i+1) > 0. Otherwise, you would have subtracted -1 from min_value.

Actually, I'm starting to dislike the whole x + !x thing. I am not sure it benefits the performance anymore, and it looks complex. We could try to

     auto const x = _sorted_morton_codes(i) ^ _sorted_morton_codes(i + 1);
     if (x)
       return x - 1;
     return min_value + i ^ (i + 1);

Does not have to be a part of this PR, though.

[aprokop]

I did a quick performance check on HACC using both DBSCAN and MST. The timings are identical to master, no performance regression.