Devtool extension authoring: EvalOnDartLibrary, how to recursively inspect an Object without causing `Sentinel <expired>` due to race conditions?

Hello!

I think I'm missing something with regards to `EvalOnDartLibrary`. I fail to see how it is possible to fully map out an object without ever risking an `` Sentinel or not loosing the ability to inspect private members.

I am aware that one trick is to do (pseudo code):

```dart
final id = eval('globalMap.register()')

try {
final content = eval('globalMap.get("$id").');
} finally {
eval('globalMap.unregister("$id")');
}
```

This prevents the ``. But afaik, prevents reading private members on the inspected object, due to `globalMap` and the private members being defined in different libraries.
(also, this will forcibly trigger late fields ; which can be undesired)

If we instead do:

```dart
final value= eval('')
final content = eval('that.', scope: {'that': value.id});
```

Then we risk that `value` will expire before `content` is resolved.

Is there something I'm missing here? Or do we need a new feature to solve this?