**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
key=DR.execution_date,
        value_range=(execution_date_gte, execution_date_lte),
    )
    base_query = _apply_range_filter(
        base_query, key=TI.start_date, value_range=(start_date_gte, start_date_lte)
    )
    base_query = _apply_range_filter(base_query, key=TI.end_date, value_range=(end_date_gte, end_date_lte))
    base_query = _apply_range_filter(base_query, key=TI.duration, value_range=(duration_gte, duration_lte))
    base_query = _apply_array_filter(base_query, key=TI.state, values=state)
    base_query = _apply_array_filter(base_query, key=TI.pool, values=pool)
    base_query = _apply_array_filter(base_query, key=TI.queue, values=queue)
    
    total_entries = base_query.with_entities(func.count('*')).scalar()
    
    base_query = base_query.join(
        SlaMiss,
        and_(
            SlaMiss.dag_id == TI.dag_id,
            SlaMiss.task_id == TI.task_id,
            SlaMiss.execution_date == TI.execution_date,
        ),
        isouter=True,
    )
    ti_query = base_query.add_entity(SlaMiss)
    task_instances = ti_query.offset(offset).limit(limit).all()
    return task_instance_collection_schema.dump(
        TaskInstanceCollection(task_instances=task_instances, total_entries=total_entries)
    )
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    [