[clang] [Clang][Sema] Use correct TemplateName when transforming TemplateSpecializationType (PR #93411)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov commented:

So After we have formed a TemplateSpecializationType, we are done with the NNS. We keep it around in an ElaboratedType for type sugar only, it should not be needed to compile the program correctly anymore.

So I think this solution violates one important aspect of our AST design.

If we still need the NNS, we have to hold-off on building the TST until we don't.

https://github.com/llvm/llvm-project/pull/93411