**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/api_connexion/endpoints/task_instance_endpoint.py
#
#
from typing import Any, List, Optional, Tuple
from flask import current_app, request
from marshmallow import ValidationError
from sqlalchemy import and_, func
from airflow.api.common.experimental.mark_tasks import set_state
from airflow.api_connexion import security
from airflow.api_connexion.exceptions import BadRequest, NotFound
from airflow.api_connexion.parameters import format_datetime, format_parameters
from airflow.api_connexion.schemas.task_instance_schema import (
    TaskInstanceCollection,
    TaskInstanceReferenceCollection,
    clear_task_instance_form,
    set_task_instance_state_form,
    task_instance_batch_form,
    task_instance_collection_schema,
    task_instance_reference_collection_schema,
    task_instance_schema,
)
from airflow.exceptions import SerializedDagNotFound
from airflow.models import SlaMiss
from airflow.models.dagrun import DagRun as DR
from airflow.models.taskinstance import TaskInstance as TI, clear_task_instances
from airflow.security import permissions
from airflow.utils.session import provide_session
from airflow.utils.state import State
@security.requires_access(