[clang] [LifetimeSafety] Warn on implicit this lifetimebound violations (PR #196926)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun approved this pull request.

Overall looks good to me, one nit inline. And there is a conflict that needs to be resolved. 

https://github.com/llvm/llvm-project/pull/196926