**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
'outlets': task.outlets,
            'params': params,
            'prev_ds': prev_ds,
            'prev_ds_nodash': prev_ds_nodash,
            'prev_execution_date': prev_execution_date,
            'prev_execution_date_success': lazy_object_proxy.Proxy(
                lambda: self.get_previous_execution_date(state=State.SUCCESS)
            ),
            'prev_start_date_success': lazy_object_proxy.Proxy(
                lambda: self.get_previous_start_date(state=State.SUCCESS)
            ),
            'run_id': run_id,
            'task': task,
            'task_instance': self,
            'task_instance_key_str': ti_key_str,
            'test_mode': self.test_mode,
            'ti': self,
            'tomorrow_ds': tomorrow_ds,
            'tomorrow_ds_nodash': tomorrow_ds_nodash,
            'ts': ts,
            'ts_nodash': ts_nodash,
            'ts_nodash_with_tz': ts_nodash_with_tz,
            'var': {
                'json': VariableJsonAccessor(),
                'value': VariableAccessor(),
            },
            'yesterday_ds': yesterday_ds,
            'yesterday_ds_nodash': yesterday_ds_nodash,
        }
    def get_rendered_template_fields(self):