BedrockAgentsRunnable invocation generates "TypeError: Object of type datetime is not JSON serializable" when enabling the traces

Hi, 

I have faced the issue when enable the traces for BedrockAgentsRunnable. In the debug I can see that `parse_agent_response` raise an error in `trace_log = json.dumps(trace_log_elements)`.


```
TypeError: Object of type datetime is not JSON serializable
```

It would be great to be able to provide a custom serializer to the config or something similar.