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

[Younan Zhang via cfe-commits]

zyn0217 wrote:

> 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 understand the point, but my thought is that we'd want as less regressions as possible; OTOH, the crash-on-invalid could also affect clangd, when the user happens to be typing something invalid.

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