[clang] [LifetimeSafety] Read lifetimebound attribute on implicit 'this' from all redeclarations (PR #176188)

[Gábor Horváth via cfe-commits]

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

I am fine landing this but would be nice to make merging work in the long term. What are the mismatching types? I wonder where the difference is coming from. 

https://github.com/llvm/llvm-project/pull/176188