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

[Balázs Benics via cfe-commits]

steakhal wrote:

> 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.

I see what you mean. I'll have a look tomorrow.
Thanks for the reviews!

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