[clang] [Clang][Sema] Refactor collection of multi-level template argument lists (PR #106585)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 commented:

Thanks for working on the refactor! I did a cursory review, mostly on the `getTemplateInstantiationArgs()` part, and the general approach looks plausible.

Re @mizvekov : this patch could supersede my refactoring work not only because of the reuse of the logic of "which next decl context to pick up for innermost arguments" and the reduction of the bool states, but my cwg2369 patch could also rely on it. So I like this patch. (Finally I don't have to rack my brain over the refactoring of it!)

https://github.com/llvm/llvm-project/pull/106585