### 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.
StateMachineType,
    StepfunctionsApi,
    StopExecutionOutput,
    TagKeyList,
    TagList,
    TagResourceOutput,
    TaskDoesNotExist,
    TaskTimedOut,
    TaskToken,
    ToleratedFailureCount,
    ToleratedFailurePercentage,
    TraceHeader,
    TracingConfiguration,
    UntagResourceOutput,
    UpdateMapRunOutput,
    UpdateStateMachineOutput,
    ValidationException,
    VersionDescription,
)
from localstack.services.stepfunctions.asl.component.state.state_execution.state_map.iteration.itemprocessor.map_run_record import (
    MapRunRecord,
)
from localstack.services.stepfunctions.asl.eval.callback.callback import (
    CallbackConsumerTimeout,
    CallbackNotifyConsumerError,
    CallbackOutcomeFailure,
    CallbackOutcomeSuccess,
)
from localstack.services.stepfunctions.asl.parse.asl_parser import (
    AmazonStateLanguageParser,