[clang] [clang-tools-extra] [Clang] Add builtins that deduplicate and sort types (PR #106730)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

Note to people reviewing this: please ensure you "hide whitespace" via `git diff -w` or the corresponding setting on GitHub. For your own sanity when looking at changes in `TreeTransform.h`, which are otherwise really complicated to validate. I've deliberately kept the code at the same place to have reasonable diffs.

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