[clang] [Clang][Parser] Build up QualifiedTemplateName for typo correction (PR #108148)

[via cfe-commits]

https://github.com/cor3ntin approved this pull request.

I think it makes sense but
 - I'd like @mizvekov to get a change to look at it
 - Even if I think the change is fairly low risk, I'm not sure a crash-on-invalid is critical enough to backport (we are at ~1 week of the release)
 
I added more people for additional feedback

https://github.com/llvm/llvm-project/pull/108148