**Apache Airflow version**:

2.0.1

**What happened**:

When clearing task across dags using `ExternalTaskMarker` the dag state of the external `DagRun` is not set to active. So cleared tasks in the external dag will not automatically start if the `DagRun` is a Failed or Succeeded state.

**What you expected to happen**:

The external `DagRun` run should also be set to Running state.

**How to reproduce it**:

Clear tasks in an external dag using an ExternalTaskMarker.


**Anything else we need to know**:

Looking at the code is has:

https://github.com/apache/airflow/blob/b23fc137812f5eabf7834e07e032915e2a504c17/airflow/models/dag.py#L1323-L1335

It seems like it intentionally calls the dag member method `set_dag_run_state` instead of letting the helper function `clear_task_insntances` set the `DagRun` state. But the member method will only change the state of `DagRun`s of dag where the original task is, while I believe `clear_task_instances` would correctly change the state of all involved `DagRun`s.

tests/sensors/test_external_task_sensor.py
task_id='head',
            external_dag_id=dag.dag_id,
            external_task_id="tail",
            execution_delta=timedelta(days=1),
            mode="reschedule",
        )
        body = DummyOperator(task_id="body")
        tail = ExternalTaskMarker(
            task_id="tail",
            external_dag_id=dag.dag_id,
            external_task_id=head.task_id,
            execution_date="{{ tomorrow_ds_nodash }}",
        )
        head >> body >> tail
    dag_bag.bag_dag(dag=dag, root_dag=dag)
    yield dag_bag
def test_clear_overlapping_external_task_marker(dag_bag_head_tail):
    dag = dag_bag_head_tail.get_dag("head_tail")
    
    first = TaskInstance(task=dag.get_task("head"), execution_date=DEFAULT_DATE)
    first.run(mark_success=True)
    for delta in range(10):
        execution_date = DEFAULT_DATE + timedelta(days=delta)
        run_tasks(dag_bag_head_tail, execution_date=execution_date)
    
    
    
    assert dag.clear(start_date=DEFAULT_DATE, dag_bag=dag_bag_head_tail) == 30
    assert dag.clear(start_date=DEFAULT_DATE, end_date=execution_date, dag_bag=dag_bag_head_tail) == 30