[ObjC][ARC] Fix non-deterministic behavior in ProvenanceAnalysis

Stop reordering the pointers passed in ProvenanceAnalysis::related based
on their values. That was causing non-determinism as the call to
relatedCheck(A, B) isn't guaranteed to return the same result as
relatedCheck(B, A).

Revert the following three commits (except the original test case in
related-check.ll):

665e4777
29586151
d877e3fe

These changes shouldn't be necessary once the call to std::swap is
removed.

Differential Revision: https://reviews.llvm.org/D150296