**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
dag_ids = []
        if include_subdags:
            
            conditions = []
            for dag in self.subdags + [self]:
                conditions.append((TI.dag_id == dag.dag_id) & TI.task_id.in_(dag.task_ids))
                dag_ids.append(dag.dag_id)
            tis = tis.filter(or_(*conditions))
        else:
            tis = session.query(TI).filter(TI.dag_id == self.dag_id)
            tis = tis.filter(TI.task_id.in_(self.task_ids))
        if include_parentdag and self.is_subdag and self.parent_dag is not None:
            dag_ids.append(self.parent_dag.dag_id)
            p_dag = self.parent_dag.sub_dag(
                task_ids_or_regex=r"^{}$".format(self.dag_id.split('.')[1]),
                include_upstream=False,
                include_downstream=True,
            )
            tis = tis.union(
                p_dag.clear(
                    start_date=start_date,
                    end_date=end_date,
                    only_failed=only_failed,
                    only_running=only_running,
                    confirm_prompt=confirm_prompt,
                    include_subdags=include_subdags,
                    include_parentdag=False,
                    dag_run_state=dag_run_state,
                    get_tis=True,
                    session=session,