### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Currently, when passing `$$.Execution.StartTime` as a parameter to a SFN lambda, it is coming in in the format `HH:MM:SS.###`.

### Expected Behavior

`$$.Execution.StartTime` should be an ISO 8601 datetime string.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

This is run in a docker compose file.

Step function definition is

```json
{
  "Comment": "Sample SFN",
  "StartAt": "SampleLambda",
  "States": {    
    "SampleLambda": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "End": true,
      "Parameters": {
        "FunctionName": "Sample-Function",
        "Payload": {
          "data": {
            "startDateTime.$": "$$.Execution.StartTime"
          }
        }
      }
    }
  }
}
```

### Environment

```markdown
- OS: Mac OS Ventura 13.6.1
- LocalStack:
LocalStack version: 3.0.1.dev
LocalStack build date: 2023-11-20
LocalStack build git hash: 3e32b438
```


### Anything else?

Thank you so much for your hard work.
if isinstance(self.state_machine, StateMachineVersion):
            state_machine_arn = self.state_machine.source_arn
            state_machine_version_arn = self.state_machine.arn
        else:
            state_machine_arn = self.state_machine.arn
            state_machine_version_arn = None
        item = ExecutionListItem(
            executionArn=self.exec_arn,
            stateMachineArn=state_machine_arn,
            name=self.name,
            status=self.exec_status,
            startDate=self.start_date,
            stopDate=self.stop_date,
        )
        if state_machine_version_arn is not None:
            item["stateMachineVersionArn"] = state_machine_version_arn
        return item
    def to_history_output(self) -> GetExecutionHistoryOutput:
        event_history: HistoryEventList = self.exec_worker.env.event_history.get_event_history()
        return GetExecutionHistoryOutput(events=event_history)
    def start(self) -> None: