**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
match against task ids (as a string, or compiled regex pattern).
        :type task_ids_or_regex: [str] or str or re.Pattern
        :param include_downstream: Include all downstream tasks of matched
            tasks, in addition to matched tasks.
        :param include_upstream: Include all upstream tasks of matched tasks,
            in addition to matched tasks.
        """
        
        
        memo = {id(self.task_dict): None, id(self._task_group): None}
        dag = copy.deepcopy(self, memo)  
        if isinstance(task_ids_or_regex, (str, RePatternType)):
            matched_tasks = [t for t in self.tasks if re.findall(task_ids_or_regex, t.task_id)]
        else:
            matched_tasks = [t for t in self.tasks if t.task_id in task_ids_or_regex]
        also_include = []
        for t in matched_tasks:
            if include_downstream:
                also_include += t.get_flat_relatives(upstream=False)
            if include_upstream:
                also_include += t.get_flat_relatives(upstream=True)
            elif include_direct_upstream:
                also_include += t.upstream_list
        
        
        dag.task_dict = {
            t.task_id: copy.deepcopy(t, {id(t.dag): dag})  
            for t in matched_tasks + also_include
        }
        def filter_task_group(group, parent_group):