Revert "[Clang] Unify interface for accessing template arguments as written...

Revert "[Clang] Unify interface for accessing template arguments as written for class/variable template specializations (#81642)"

This reverts commit 7115ed0f.

This commit broke several LLDB tests.

https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/as-lldb-cmake/3480/