message: buck2: starlark-rust: expose `OwnedFrozenValue::owner`
  Summary: This can be helpful to e.g. get stats about said owner.
diff: @@ -114,6 +114,11 @@ impl OwnedFrozenValue {
  })
  }
  + /// Obtain a reference to the FrozenHeap that owns this value.
  + pub fn owner(&self) -> &FrozenHeapRef {
  + &self.owner
  + }
  +
  /// Obtain direct access to the [`FrozenValue`] that lives inside. If you drop all
  /// references to the [`FrozenHeap`] keeping it alive, any code using the [`FrozenValue`]
  /// is likely to segfault. If possible use [`value`](OwnedFrozenValue::value) or
  