### 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,
    ) -> DescribeStateMachineForExecutionOutput:
        state_machine: StateMachineInstance = self.state_machine
        state_machine_arn = (
            state_machine.source_arn
            if isinstance(state_machine, StateMachineVersion)
            else state_machine.arn
        )
        out = DescribeStateMachineForExecutionOutput(
            stateMachineArn=state_machine_arn,
            name=state_machine.name,
            definition=state_machine.definition,
            roleArn=self.role_arn,
            
            updateDate=state_machine.create_date,
        )
        revision_id = self.state_machine.revision_id
        if self.state_machine.revision_id:
            out["revisionId"] = revision_id
        return out
    def to_execution_list_item(self) -> ExecutionListItem: