### 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.name = state_props.name
        self.state_type = state_props.get(StateType)
        self.continue_with = (
            ContinueWithEnd() if state_props.get(End) else ContinueWithNext(state_props.get(Next))
        )
        self.comment = state_props.get(Comment)
        self.input_path = state_props.get(InputPath) or InputPath(InputPath.DEFAULT_PATH)
        self.output_path = state_props.get(OutputPath) or OutputPath(OutputPath.DEFAULT_PATH)
    def _set_next(self, env: Environment) -> None:
        if env.next_state_name != self.name:
            
            return
        if isinstance(self.continue_with, ContinueWithNext):
            env.next_state_name = self.continue_with.next_state.name
        elif isinstance(self.continue_with, ContinueWithEnd):  
            env.set_ended()
        else:
            LOG.error(f"Could not handle ContinueWith type of '{type(self.continue_with)}'.")
    def _get_state_entered_event_details(self, env: Environment) -> StateEnteredEventDetails: