[clang] [clang-tools-extra] [clang]: Propagate `*noreturn` attributes in `CFG` (PR #146355)

[Gábor Horváth via cfe-commits]

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

I think this is a good change in general, but I wonder what is the performance impact. 
Note that clang CFGs have many clients and some of them might not need this information. If there is a measurable performance cost, we might want to put this behind a flag, especially because there are some on by default warnings that build the CFG. 

https://github.com/llvm/llvm-project/pull/146355