**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
)
                        ti.task = task
                        if recursion_depth == 0:
                            
                            
                            max_recursion_depth = task.recursion_depth
                        if recursion_depth + 1 > max_recursion_depth:
                            
                            raise AirflowException(
                                "Maximum recursion depth {} reached for {} {}. "
                                "Attempted to clear too many tasks "
                                "or there may be a cyclic dependency.".format(
                                    max_recursion_depth, ExternalTaskMarker.__name__, ti.task_id
                                )
                            )
                        ti.render_templates()
                        external_tis = session.query(TI).filter(
                            TI.dag_id == task.external_dag_id,
                            TI.task_id == task.external_task_id,
                            TI.execution_date == pendulum.parse(task.execution_date),
                        )
                        for tii in external_tis:
                            if not dag_bag:
                                dag_bag = DagBag(read_dags_from_db=True)
                            external_dag = dag_bag.get_dag(tii.dag_id)
                            if not external_dag:
                                raise AirflowException(f"Could not find dag {tii.dag_id}")
                            downstream = external_dag.sub_dag(
                                task_ids_or_regex=fr"^{tii.task_id}$",
                                include_upstream=False,