[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:

I'd like someone to review the AST matcher changes (the code owner listed in `CodeOwners.rst` appears to be inactive).

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