### 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.
BASE_DATE = timezone.datetime(2022, 7, 20, 20)
        test_dag_id = "test_get_task_instances_before"
        test_task_id = "the_task"
        test_dag = DAG(dag_id=test_dag_id, start_date=BASE_DATE)
        EmptyOperator(task_id=test_task_id, dag=test_dag)
        session = settings.Session()
        def dag_run_before(delta_h=0, type=DagRunType.SCHEDULED):
            dagrun = test_dag.create_dagrun(
                state=State.SUCCESS, run_type=type, run_id=f"test_{delta_h}", session=session
            )
            dagrun.start_date = BASE_DATE + timedelta(hours=delta_h)
            dagrun.execution_date = BASE_DATE + timedelta(hours=delta_h)
            return dagrun
        dr1 = dag_run_before(delta_h=-1, type=DagRunType.MANUAL)  
        dr2 = dag_run_before(delta_h=-2, type=DagRunType.MANUAL)  
        dr3 = dag_run_before(delta_h=-3, type=DagRunType.MANUAL)  
        dr4 = dag_run_before(delta_h=-4, type=DagRunType.MANUAL)  
        dr5 = dag_run_before(delta_h=-5)  
        dr6 = dag_run_before(delta_h=-6)  
        dr7 = dag_run_before(delta_h=-7)  
        dr8 = dag_run_before(delta_h=-8)  
        session.commit()
        REF_DATE = BASE_DATE
        assert set([dr.run_id for dr in [dr1]]) == set(
            [
                ti.run_id
                for ti in test_dag.get_task_instances_before(base_date=REF_DATE, num=1, session=session)
            ]