### 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.
name: Final[str]
    role_arn: Final[Arn]
    exec_arn: Final[Arn]
    account_id: str
    region_name: str
    state_machine: Final[StateMachineInstance]
    start_date: Final[Timestamp]
    input_data: Final[Optional[dict]]
    input_details: Final[Optional[CloudWatchEventsExecutionDataDetails]]
    trace_header: Final[Optional[TraceHeader]]
    exec_status: Optional[ExecutionStatus]
    stop_date: Optional[Timestamp]
    output: Optional[SensitiveData]
    output_details: Optional[CloudWatchEventsExecutionDataDetails]
    error: Optional[SensitiveError]
    cause: Optional[SensitiveCause]
    exec_worker: Optional[ExecutionWorker]
    def __init__(