[clang] [Clang] Add wraps attribute (for granular integer overflow handling) (PR #86618)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Forbidding usage in C++ probably avoids the worst of the canonical-type issues, but there's still some potential for weird results.  Particularly with type merging; for example, if you write `a ? (wrap_int)x : 1`, is the result a wrapping type?

https://github.com/llvm/llvm-project/pull/86618