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

[Gábor Spaits via cfe-commits]

spaits wrote:

Thank you @Sirraide for reviewing. I will wait a few hours if other also want to take a look at this, then I will squash the commits and merge the changes.

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