**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
job_ids.append(ti.job_id)
        else:
            task_id = ti.task_id
            if dag and dag.has_task(task_id):
                task = dag.get_task(task_id)
                ti.refresh_from_task(task)
                task_retries = task.retries
                ti.max_tries = ti.try_number + task_retries - 1
            else:
                
                
                
                
                ti.max_tries = max(ti.max_tries, ti.prev_attempted_tries)
            ti.state = State.NONE
            session.merge(ti)
        task_id_by_key[ti.dag_id][ti.execution_date][ti.try_number].add(ti.task_id)
    if task_id_by_key:
        
        
        
        
        
        
        conditions = or_(
            and_(
                TR.dag_id == dag_id,
                or_(
                    and_(
                        TR.execution_date == execution_date,