[ObjC][ARC] Use the addresses of the ARC runtime functions instead of

integer 0/1 for the operand of bundle "clang.arc.attachedcall"

This should make it easier to understand what the IR is doing and also
simplify some of the passes as they no longer have to translate the
integer values to the runtime functions.

Differential Revision: https://reviews.llvm.org/D102996