### 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.
self.update_event = threading.Event()
        (
            map_state_machine_arn,
            map_run_arn,
        ) = self._generate_map_run_arns(state_machine_arn=state_machine_arn)
        self.map_run_arn = map_run_arn
        self.map_state_machine_arn = map_state_machine_arn
        self.execution_arn = execution_arn
        self.max_concurrency = max_concurrency
        self.execution_counter = ExecutionCounter()
        self.item_counter = ItemCounter()
        self.start_date = datetime.datetime.now()
        self.status = MapRunStatus.RUNNING
        self.stop_date = None
        self.tolerated_failure_count = 0
        self.tolerated_failure_percentage = 0.0
    @staticmethod
    def _generate_map_run_arns(state_machine_arn: Arn) -> tuple[LongArn, LongArn]:
        
        
        
        
        map_run_arn = state_machine_arn.replace(":stateMachine:", ":mapRun:")
        part_1 = long_uid()
        map_run_arn = f"{map_run_arn}/{part_1}:{long_uid()}"
        return f"{state_machine_arn}/{part_1}", map_run_arn
    def set_stop(self, status: MapRunStatus):