**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
import warnings
from collections import defaultdict
from datetime import datetime, timedelta
from tempfile import NamedTemporaryFile
from typing import IO, Any, Dict, Iterable, List, NamedTuple, Optional, Tuple, Union
from urllib.parse import quote
import dill
import jinja2
import lazy_object_proxy
import pendulum
from jinja2 import TemplateAssertionError, UndefinedError
from sqlalchemy import Column, Float, Index, Integer, PickleType, String, and_, func, or_
from sqlalchemy.exc import OperationalError
from sqlalchemy.orm import reconstructor, relationship
from sqlalchemy.orm.session import Session
from sqlalchemy.sql.elements import BooleanClauseList
from airflow import settings
from airflow.configuration import conf
from airflow.exceptions import (
    AirflowException,
    AirflowFailException,
    AirflowRescheduleException,
    AirflowSkipException,
    AirflowSmartSensorException,
    AirflowTaskTimeout,
)
from airflow.models.base import COLLATION_ARGS, ID_LEN, Base
from airflow.models.log import Log
from airflow.models.taskfail import TaskFail
from airflow.models.taskreschedule import TaskReschedule