[clang] [clang] implement current CWG direction for string literal comparisons in constant evaluation (PR #109208)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

In case I don't get a chance to look at this in more detail right away can you please reference specific CWG issues in the summary and in comments in the code? Thank you.

https://github.com/llvm/llvm-project/pull/109208