[clang] [Lifetime Safety] Highlight lifetimebound calls in alias chain diagnostics (PR #206337)

[Gábor Horváth via cfe-commits]

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

I think we might be missing a test where we take the `unnamed` branch for the reporting.

But overall it looks great for me. Once @NeKon69 is also happy with the PR, I think we can merge this. 

I know we asked for a lot of changes and iterations and sometimes my comments were not the clearest. Thanks a lot for sticking around and putting in the hard work, this is a great improvement for the readability of the diagnostics! 

https://github.com/llvm/llvm-project/pull/206337