### Body

There are some use cases where users want to trigger new DAG run as soon as one finished. This is a request I've seen several times with some variations (for example like this [Stackoverflow question](https://stackoverflow.com/q/75623153/14624409)) but the basic request is the same.

The workaround users do to get such functionality is place `TriggerDagRunOperator` as last task of their DAG invoking the same DAG:

```
from datetime import datetime

from airflow import DAG
from airflow.operators.empty import EmptyOperator
from airflow.operators.trigger_dagrun import TriggerDagRunOperator

with DAG(
    dag_id="example",
    start_date=datetime(2023, 1, 1,),
    catchup=False,
    schedule=None,
) as dag:
    task = EmptyOperator(task_id="first")
    trigger = TriggerDagRunOperator(
        task_id="trigger",
        trigger_dag_id="example",
    )

    task >> trigger

```

As you can see this works nicely:
![Screenshot 2023-03-03 at 14 20 51](https://user-images.githubusercontent.com/45845474/222718862-dfde8a41-24b6-4991-b318-b7f9784514f6.png)

My suggestion is to add first class support for this use case, so the above example will be changed to:

```

from datetime import datetime

from airflow import DAG
from airflow.operators.empty import EmptyOperator
from airflow.operators.trigger_dagrun import TriggerDagRunOperator

with DAG(
    dag_id="example",
    start_date=datetime(2023, 1, 1,),
    catchup=False,
    schedule="@continues",
) as dag:
    task = EmptyOperator(task_id="first")
```

I guess it won't exactly be `"@continues"` but more likely new [ScheduleArg](https://github.com/apache/airflow/blob/8b8552f5c4111fe0732067d7af06aa5285498a79/airflow/models/dag.py#L127) type but I show it like that just for simplification of the idea.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
RemovedInAirflow3Warning,
                stacklevel=2,
            )
        validate_key(dag_id)
        self._dag_id = dag_id
        if concurrency:
            
            warnings.warn(
                "The 'concurrency' parameter is deprecated. Please use 'max_active_tasks'.",
                RemovedInAirflow3Warning,
                stacklevel=2,
            )
            max_active_tasks = concurrency
        self._max_active_tasks = max_active_tasks
        self._pickle_id: int | None = None
        self._description = description
        
        back = sys._getframe().f_back
        self.fileloc = back.f_code.co_filename if back else ""
        self.task_dict: dict[str, Operator] = {}
        
        tz = None
        if start_date and start_date.tzinfo:
            tzinfo = None if start_date.tzinfo else settings.TIMEZONE
            tz = pendulum.instance(start_date, tz=tzinfo).timezone
        elif "start_date" in self.default_args and self.default_args["start_date"]:
            date = self.default_args["start_date"]
            if not isinstance(date, datetime):
                date = timezone.parse(date)
                self.default_args["start_date"] = date