[clang] [clang-tools-extra] [clang] Concepts: support pack expansions for type constraints (PR #132626)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 commented:

And, I think this also merits a compile-time regression test - we now hold more bytes when instantiating the constraint

https://github.com/llvm/llvm-project/pull/132626