**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
"""
    Create a DagBag with DAGs looking like this. The dotted lines represent external dependencies
    set up using ExternalTaskMarker and ExternalTaskSensor.
    dag_0:   task_a_0 >> task_b_0
                             |
                             |
    dag_1:                   ---> task_a_1 >> task_b_1
                                                  |
                                                  |
    dag_2:                                        ---> task_a_2 >> task_b_2
                                                                       |
                                                                       |
    dag_3:                                                             ---> task_a_3 >> task_b_3
    """
    dag_bag = DagBag(dag_folder=DEV_NULL, include_examples=False)
    dag_0 = DAG("dag_0", start_date=DEFAULT_DATE, schedule_interval=None)
    task_a_0 = DummyOperator(task_id="task_a_0", dag=dag_0)
    task_b_0 = ExternalTaskMarker(
        task_id="task_b_0", external_dag_id="dag_1", external_task_id="task_a_1", recursion_depth=3, dag=dag_0
    )
    task_a_0 >> task_b_0
    dag_1 = DAG("dag_1", start_date=DEFAULT_DATE, schedule_interval=None)
    task_a_1 = ExternalTaskSensor(
        task_id="task_a_1", external_dag_id=dag_0.dag_id, external_task_id=task_b_0.task_id, dag=dag_1
    )
    task_b_1 = ExternalTaskMarker(
        task_id="task_b_1", external_dag_id="dag_2", external_task_id="task_a_2", recursion_depth=2, dag=dag_1
    )
    task_a_1 >> task_b_1
    dag_2 = DAG("dag_2", start_date=DEFAULT_DATE, schedule_interval=None)