[BasicAA] Fix order in which we pass MemoryLocations to alias()

D98718 caused the order of Values/MemoryLocations we pass to alias() to
be significant due to storing the offset in the PartialAlias case. But
some callers weren't audited and were still passing swapped arguments,
causing the returned PartialAlias offset to be negative in some
cases. For example, the newly added unittests would return -1
instead of 1.

Fixes #55343, a miscompile.

Reviewed By: asbirlea, nikic

Differential Revision: https://reviews.llvm.org/D125328