[clang] [CIR] Upstream LabelOp (PR #152802)

[Morris Hafner via cfe-commits]

mmha wrote:

Can you add tests where you put a label in some unreachable code?

```c++
void after_return() {
  return;
  label:
}

void after_throw() {
  throw 0;
  label:
}
```

https://github.com/llvm/llvm-project/pull/152802