[clang] [Clang][NFCI] Slightly refactor getTemplateInstantiationArgs() (PR #102922)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov commented:

I think I'd need to see how you would use it, to say if this would be the best approach.

It's not clear to me why we would want to navigate to a DC that is unrelated to the passed ND.

Can we at least assert the DC would be a parent (Lexical or Semantic)

https://github.com/llvm/llvm-project/pull/102922