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

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@AaronBallman release note added (feel free to suggest any changes to it :))

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