**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
self.set_duration()
        Stats.incr(f'operator_failures_{task.task_type}', 1, 1)
        Stats.incr('ti_failures')
        if not test_mode:
            session.add(Log(State.FAILED, self))
        
        session.add(TaskFail(task, self.execution_date, self.start_date, self.end_date))
        
        
        
        
        
        
        
        
        
        if force_fail or not self.is_eligible_to_retry():
            self.state = State.FAILED
            if force_fail:
                log_message = "Immediate failure requested. Marking task as FAILED."
            else:
                log_message = "Marking task as FAILED."
            email_for_state = task.email_on_failure
        else:
            self.state = State.UP_FOR_RETRY
            log_message = "Marking task as UP_FOR_RETRY."
            email_for_state = task.email_on_retry
        self.log.info(
            '%s dag_id=%s, task_id=%s, execution_date=%s, start_date=%s, end_date=%s',
            log_message,