fix(smart_sensor): runtime and unbound var errors

[shivanshs9]

Closes #14770

---

Fixes various runtime errors in smart sensor:

1. UnboundLocalError

UnboundLocalError: local variable 'query_result' referenced before assignment
  File "airflow/sensors/smart_sensor.py", line 639, in _execute_sensor_work
    self._mark_multi_state(
  File "airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "airflow/sensors/smart_sensor.py", line 470, in _mark_multi_state
    self.log.info("Marked %s tasks out of %s to state %s", count_marked, len(query_result), state)

2. RuntimeError

  File "airflow/sentry.py", line 159, in wrapper
    return func(task_instance, *args, session=session, **kwargs)
  File "airflow/models/taskinstance.py", line 1112, in _run_raw_task
    self._prepare_and_execute_task_with_callbacks(context, task)
  File "airflow/models/taskinstance.py", line 1285, in _prepare_and_execute_task_with_callbacks
    result = self._execute_task(context, task_copy)
  File "airflow/models/taskinstance.py", line 1315, in _execute_task
    result = task_copy.execute(context=context)
  File "airflow/sensors/smart_sensor.py", line 736, in execute
    self.flush_cached_sensor_poke_results()
  File "airflow/sensors/smart_sensor.py", line 681, in flush_cached_sensor_poke_results
    for ti_key, sensor_exception in self.cached_sensor_exceptions.items():

3. InvalidRequestError (should be related to 1)

InvalidRequestError: This Session's transaction has been rolled back due to a previous exception during flush. To begin a new transaction with this Session, first issue Session.rollback(). Original exception was: Timeout, PID: 24375 (Background on this error at: http://sqlalche.me/e/13/7s2a)
  File "airflow/sensors/smart_sensor.py", line 639, in _execute_sensor_work
    self._mark_multi_state(
  File "airflow/utils/session.py", line 65, in wrapper
    return func(*args, session=session, **kwargs)
  File "contextlib.py", line 120, in __exit__
    next(self.gen)
  File "airflow/utils/session.py", line 32, in create_session
    session.commit()
  File "sqlalchemy/orm/session.py", line 1046, in commit
    self.transaction.commit()
  File "sqlalchemy/orm/session.py", line 502, in commit
    self._assert_active(prepared_ok=True)
  File "sqlalchemy/orm/session.py", line 289, in _assert_active
    raise sa_exc.InvalidRequestError(

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[kaxil]

cc @YingboWang @KevinYang21

[kaxil]

@shivanshs9 Can you rebase your PR on Main please and fix the conflicts

[shivanshs9]

@kaxil I rebased the PR and apparently the RuntimeError is fixed in another PR - #14920, explained in this comment.

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.