[clang] [analyzer] Fix [[clang::suppress]] for template instantiations (PR #168954)

[Artem Dergachev via cfe-commits]

https://github.com/haoNoQ approved this pull request.

I'm somewhat surprised that it's necessary to visit template instantiations. This machine simply memorizes source locations. Template instantiations have the same source locations as the template itself right? (...right? 😳)

LGTM because I'm sure there's a perfectly reasonable explanation for that.

https://github.com/llvm/llvm-project/pull/168954