**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/taskinstance.py
or_(
                            and_(TR.try_number == try_number, TR.task_id.in_(task_ids))
                            for try_number, task_ids in task_tries.items()
                        ),
                    )
                    for execution_date, task_tries in dates.items()
                ),
            )
            for dag_id, dates in task_id_by_key.items()
        )
        delete_qry = TR.__table__.delete().where(conditions)
        session.execute(delete_qry)
    if job_ids:
        from airflow.jobs.base_job import BaseJob
        for job in session.query(BaseJob).filter(BaseJob.id.in_(job_ids)).all():  
            job.state = State.SHUTDOWN
    if activate_dag_runs and tis:
        from airflow.models.dagrun import DagRun  
        drs = (
            session.query(DagRun)
            .filter(
                DagRun.dag_id.in_({ti.dag_id for ti in tis}),
                DagRun.execution_date.in_({ti.execution_date for ti in tis}),
            )
            .all()
        )
        for dr in drs:
            dr.state = State.RUNNING
            dr.start_date = timezone.utcnow()
class TaskInstanceKey(NamedTuple):