[ObjC][ProvenanceEval] Only evaluate pointers (#136876)
I believe this pass should only be calling PA.related() on pointer
arguments -- the operation is not really meaningful for non-pointers.
I've adjusted the test to use ptr loads instead of i8 loads, which I
believe aligns with how these special globals would actually be used,
and which is probably what this was intending to test.
Ran into this while trying to eliminate illegal non-pointer AA queries.
