[clang] clang: Make the type_info builtin declaration a singleton (PR #151277)

[Andrey Ali Khan Bolshakov via cfe-commits]

bolshakov-a wrote:

I've noticed that this PR changed the tag type kind of the implicit `type_info` from `class` to `struct`. I don't know if it has any bad consequences, but it looks inconsistent with the definition of `std::type_info`.

https://github.com/llvm/llvm-project/pull/151277