### 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.
aborted: Final[Counter]
    failed: Final[Counter]
    pending: Final[Counter]
    results_written: Final[Counter]
    running: Final[Counter]
    succeeded: Final[Counter]
    timed_out: Final[Counter]
    total: Final[Counter]
    def __init__(self):
        self.aborted = Counter()
        self.failed = Counter()
        self.pending = Counter()
        self.results_written = Counter()
        self.running = Counter()
        self.succeeded = Counter()
        self.timed_out = Counter()
        self.total = Counter()
class ExecutionCounter(ProgressCounter):
    def describe(self) -> MapRunExecutionCounts:
        return MapRunExecutionCounts(
            aborted=self.aborted.get(),
            failed=self.failed.get(),
            pending=self.pending.get(),
            resultsWritten=self.results_written.get(),
            running=self.running.get(),
            succeeded=self.succeeded.get(),
            timedOut=self.timed_out.get(),
            total=self.total.get(),
        )
class ItemCounter(ProgressCounter):