[clang] [clang-tools-extra] [Clang] Unify interface for accessing template arguments as written for class/variable template specializations (PR #81642)

[Erich Keane via cfe-commits]

erichkeane wrote:

> Ping @AaronBallman

Aaron is on vacation this week, is there feedback from him that you're looking for? 

https://github.com/llvm/llvm-project/pull/81642