Refactor space filling curves surrounding code

[aprokop]

• Fix getGeometry for prvalues If a passed function argument is a prvalue, it will be destroyed once we return, as returning a reference to its member does not extend its lifetime.
• Move projectOntoSpaceFillingCurve from ArborX_TreeConstruction.hpp to ArborX_SpaceFillingCurve.hpp It will also be used by the tree traversal now
• Change signature of projectOntoSpaceFillingCurve to return linear ordering This avoids a lot of boilerplate code to determine the type. We currently have zero benefit from passing indices as the last argument.
• Add computeSpaceFillingCurvePermutation that combines projectOntoSpaceFillingCurve with sorting to further reduce the amount of code
• Added PredicateIndexables to easily iterate over predicate geometries