[lldb] [clang] [NFC][Clang] Improve const correctness for IdentifierInfo (PR #79365)

[via cfe-commits]

cor3ntin wrote:

I think this is nice, thanks!

I'd like to wait a few weeks before we land it, I'm afraid these changes (which do contain some small white spaces-only changes too) might disrupt the release process as lot of cherry-picking between main and the llvm18 branch are happening and we should minimize the opportunity for merge conflicts.

https://github.com/llvm/llvm-project/pull/79365