[clang] [PAC][clang] Implement address/type discrimination for VTT vtable pointers (PR #205808)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

@chbessonova congrats! keep an eye on the bots for a while just in case this does bork something (I don't believe it will, but it's always good to be safe)

https://github.com/llvm/llvm-project/pull/205808