[clang] [clang-tools-extra] [Clang] Add __type_list_dedup builtin to deduplicate types in templat… (PR #106730)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

RFC for this change: https://discourse.llvm.org/t/rfc-adding-builtin-for-deduplicating-type-lists/80986

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