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

[Bill Wendling via cfe-commits]

bwendling 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?

I had a similar question in the general case: is the annotation contagious?

```
int foo(wrap_int x, int a, int b, int c) {
  if (x + a + b < c)
    return 0;
  return 1;
}
```

The `x + a` is checked, but is that result checked when added to `b`?

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