[clang-tools-extra] [clang] Reapply "[Clang][Sema] Diagnose unexpanded packs in the template argument lists of function template specializations" (#76876) (PR #76915)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

@cor3ntin @erichkeane if either of you could merge that that would be appreciated :)

https://github.com/llvm/llvm-project/pull/76915