[clang] [clang-tools-extra] [llvm] [Clang] Add __builtin_type_pack_dedup template to deduplicate types in template arguments (PR #106730)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

I have also left a few comments in the parallel discussion on the RFC.

https://github.com/llvm/llvm-project/pull/106730