getRangePolicy iterates over the whole view, regardless of overallocation

OPALX uses getRangePolicy(Rview) in a few places. At the moment, this does not seem to lead to bugs, but is probably bad for performance. For example here, we have:

auto Rview = pc->R.getView();
Kokkos::parallel_reduce(..., ippl::getRangePolicy(Rview) ...

However, Rview is just the underlying view of the attribute, which might be double the size of the number of particles for an overallocation of 2. Using getLocalNum() (like here) makes more sense in my opinion.