[AI Evaluation] How should MEAI.Eval be used with GetStreamingResponseAsync

The examples I've seen for using the Eval library all use `IChatClient.GetResponseAsync` which returns a `ChatResponse`. The `IChatClient.GetStreamingResponseAsync` method returns a `ChatResponseUpdate`. So in order to use the evaluation library I need to do:
```csharp
StringBuilder builder = new();
await foreach (var msg in IChatClient.GetStreamingResponseAsync())
{
builder.Append(msg.Text);
}
scenarioRun.EvaluateAsync(chatMessages, new ChatResponse(new ChatMessage(ChatRole.Assistant, builder.ToString())
```