**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/models/dag.py
session.query(DagRun.dag_id, func.count('*'))
            .filter(
                DagRun.dag_id.in_(existing_dag_ids),
                DagRun.state == State.RUNNING,  
                DagRun.external_trigger == expression.false(),
            )
            .group_by(DagRun.dag_id)
            .all()
        )
        for orm_dag in sorted(orm_dags, key=lambda d: d.dag_id):
            dag = dag_by_ids[orm_dag.dag_id]
            if dag.is_subdag:
                orm_dag.is_subdag = True
                orm_dag.fileloc = dag.parent_dag.fileloc  
                orm_dag.root_dag_id = dag.parent_dag.dag_id  
                orm_dag.owners = dag.parent_dag.owner  
            else:
                orm_dag.is_subdag = False
                orm_dag.fileloc = dag.fileloc
                orm_dag.owners = dag.owner
            orm_dag.is_active = True
            orm_dag.last_parsed_time = timezone.utcnow()
            orm_dag.default_view = dag.default_view
            orm_dag.description = dag.description
            orm_dag.schedule_interval = dag.schedule_interval
            orm_dag.concurrency = dag.concurrency
            orm_dag.has_task_concurrency_limits = any(t.task_concurrency is not None for t in dag.tasks)
            orm_dag.calculate_dagrun_date_fields(
                dag,
                most_recent_dag_runs.get(dag.dag_id),