[clang] [CIR] Make ClangIR compatible with latest nested name specifier AST representation (PR #152846)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

I think @darkbuck comitted a similar solution before I land 😕, I will rebase and land the diff from the code review comments

https://github.com/llvm/llvm-project/pull/152846