[llvm] [llvm] Add NodeMetadata::optUnsafeEdges (NFC) (PR #137539)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> Can we replace the member with OwningArrayRef instead?

I don't think so.  The array could be reallocated in the middle of lifetime:

```
  void setup(const Vector& Costs) {
    NumOpts = Costs.getLength() - 1;
    OptUnsafeEdges = std::unique_ptr<unsigned[]>(new unsigned[NumOpts]());
  }
```


https://github.com/llvm/llvm-project/pull/137539