[clang] Reapply "[Clang][Sema] Refactor collection of multi-level template argument lists (#106585)" (PR #111173)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

Yeah, I think its only user was reverted a while ago, but should be merged back eventually.

https://github.com/llvm/llvm-project/pull/111173