[clang] [analyzer] Introduce the invalidation artifact symbol (PR #207155)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun commented:

Added some high level comments while skimming through. I think conserving more information about invalidation is something that we want to have in general. But the details will be a bit subtle to get right. 

https://github.com/llvm/llvm-project/pull/207155