[clang] [clang-tools-extra] Reapply "[Clang] Unify interface for accessing template arguments as written for class/variable template specializations (#81642)" (PR #91393)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@adrian-prantl While I'm not 100% certain of this, I _think_ modules are cached between test runs for LLDB (the only way I was able to reproduce the crash was by precompiling modules with clang built from the commit before this one, and then deserializing with clang built from this commit). So I _think_ the solution is to bump the AST file major version number, but I'm still looking into it.

https://github.com/llvm/llvm-project/pull/91393