**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.

airflow/api_connexion/endpoints/task_instance_endpoint.py
raise NotFound(error_message)
    except SerializedDagNotFound:
        
        raise NotFound(error_message)
    task_id = data['task_id']
    task = dag.task_dict.get(task_id)
    if not task:
        error_message = f"Task ID {task_id} not found"
        raise NotFound(error_message)
    tis = set_state(
        tasks=[task],
        execution_date=data["execution_date"],
        upstream=data["include_upstream"],
        downstream=data["include_downstream"],
        future=data["include_future"],
        past=data["include_past"],
        state=data["new_state"],
        commit=not data["dry_run"],
    )
    execution_dates = {ti.execution_date for ti in tis}
    execution_date_to_run_id_map = dict(
        session.query(DR.execution_date, DR.run_id).filter(
            DR.dag_id == dag_id, DR.execution_date.in_(execution_dates)
        )
    )
    tis_with_run_id = [(ti, execution_date_to_run_id_map.get(ti.execution_date)) for ti in tis]
    return task_instance_reference_collection_schema.dump(
        TaskInstanceReferenceCollection(task_instances=tis_with_run_id)
    )