Sacado: Fix calculation of fad size in common_view_alloc_prop for mixed view specs

Created by: etphipp

For issue #3679 (closed). While converting Panzer to use hierarchical-dfad, @rppawlo ran into an issue with Intrepid2 that was using common_view_alloc_prop to create a non-contiguous view using contiguous view arguments. The logic used within common_view_alloc_prop didn't allow for this. I fixed this by allowing the code that pulls out the fad dimension to work with any specialization tag, not just the one the constructed view has. I also added a unit test to test this behavior.