### 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, context: RequestContext, name: str
    ) -> Optional[StateMachineInstance]:
        state_machines: list[StateMachineInstance] = list(
            self.get_store(context).state_machines.values()
        )
        for state_machine in state_machines:
            if isinstance(state_machine, StateMachineRevision) and state_machine.name == name:
                return state_machine
        return None
    @staticmethod
    def _validate_definition(definition: str):
        
        
        try:
            AmazonStateLanguageParser.parse(definition)
        except ASLParserException as asl_parser_exception:
            invalid_definition = InvalidDefinition()
            invalid_definition.message = repr(asl_parser_exception)
            raise invalid_definition
        except Exception as exception:
            exception_name = exception.__class__.__name__
            exception_args = list(exception.args)
            invalid_definition = InvalidDefinition()
            invalid_definition.message = (
                f"Error={exception_name} Args={exception_args} in definition '{definition}'."
            )
            raise invalid_definition
    def create_state_machine(