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

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

FYI I just realized the Final parameter is not wired up to the Collecter. It appertains to the Innermost argument.

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