**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
if dag_run and dag_run.external_trigger:
            prev_execution_date = self.execution_date
            next_execution_date = self.execution_date
        else:
            prev_execution_date = task.dag.previous_schedule(self.execution_date)
            next_execution_date = task.dag.following_schedule(self.execution_date)
        next_ds = None
        next_ds_nodash = None
        if next_execution_date:
            next_ds = next_execution_date.strftime('%Y-%m-%d')
            next_ds_nodash = next_ds.replace('-', '')
            next_execution_date = pendulum.instance(next_execution_date)
        prev_ds = None
        prev_ds_nodash = None
        if prev_execution_date:
            prev_ds = prev_execution_date.strftime('%Y-%m-%d')
            prev_ds_nodash = prev_ds.replace('-', '')
            prev_execution_date = pendulum.instance(prev_execution_date)
        ds_nodash = ds.replace('-', '')
        ts_nodash = self.execution_date.strftime('%Y%m%dT%H%M%S')
        ts_nodash_with_tz = ts.replace('-', '').replace(':', '')
        yesterday_ds_nodash = yesterday_ds.replace('-', '')
        tomorrow_ds_nodash = tomorrow_ds.replace('-', '')
        ti_key_str = f"{task.dag_id}__{task.task_id}__{ds_nodash}"
        if task.params:
            params.update(task.params)
        if conf.getboolean('core', 'dag_run_conf_overrides_params'):
            self.overwrite_params_with_dag_run_conf(params=params, dag_run=dag_run)
        class VariableAccessor: