### Apache Airflow version

2.2.0b2 (beta snapshot)

### Operating System

ubuntu 20.04

### Versions of Apache Airflow Providers

n/a

### Deployment

Virtualenv installation

### Deployment details

pip install /path/to/airflow/src

### What happened

Given any DAG initialized with: `schedule_interval=None`

Run `airflow dags test mydagname $(date +%Y-%m-%d)` and get an error:

```
INFO - No run dates were found for the given dates and dag interval.
```

This behavior changed in https://github.com/apache/airflow/pull/15397, it used to trigger a backfill dagrun at the given date.

### What you expected to happen

I expected a backfill dagrun with the given date, regardless of whether it fit into the `schedule_interval`.

If AIP-39 made that an unrealistic expectation, then I'd hope for some way to define unscheduled dags which can still be tested from the command line (which, so far as I know, is the fastest way to iterate on a DAG.).

As it is, I keep changing `schedule_interval` back and forth depending on whether I want to iterate via `astro dev start` (which tolerates `None` but does superfluous work if the dag is scheduled) or via `airflow dags test ...` (which doesn't tolerate `None`).

### How to reproduce

Initialize a DAG with: `schedule_interval=None` and run it via `airflow dags test mydagname $(date +%Y-%m-%d)`

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/jobs/backfill_job.py
self._execute_dagruns(
                    dagrun_infos=dagrun_infos_to_process,
                    ti_status=ti_status,
                    executor=executor,
                    pickle_id=pickle_id,
                    start_date=start_date,
                    session=session,
                )
                remaining_dates = ti_status.total_runs - len(ti_status.executed_dag_run_dates)
                err = self._collect_errors(ti_status=ti_status, session=session)
                if err:
                    raise BackfillUnfinished(err, ti_status)
                if remaining_dates > 0:
                    self.log.info(
                        "max_active_runs limit for dag %s has been reached "
                        " - waiting for other dag runs to finish",
                        self.dag_id,
                    )
                    time.sleep(self.delay_on_limit_secs)
        except (KeyboardInterrupt, SystemExit):
            self.log.warning("Backfill terminated by user.")
            
            
            self._set_unfinished_dag_runs_to_failed(ti_status.active_runs)
        finally:
            session.commit()
            executor.end()
        self.log.info("Backfill done. Exiting.")
    @provide_session
    def reset_state_for_orphaned_tasks(self, filter_by_dag_run=None, session=None):