[clang] [Sema]Use tag name lookup for class names (PR #112166)

[Gábor Spaits via cfe-commits]

spaits wrote:

The windows CI passes. The linux CI fails, but it also fails on other clang fronted PRs (see https://github.com/llvm/llvm-project/pull/112289 for example). I think this failure is unrelated to this PR. I will merge this.

https://github.com/llvm/llvm-project/pull/112166