### 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/models/dag.py
return None
        if isinstance(last_automated_dagrun, datetime):
            warnings.warn(
                "Passing a datetime to DAG.next_dagrun_info is deprecated. Use a DataInterval instead.",
                DeprecationWarning,
                stacklevel=2,
            )
            data_interval = self.infer_automated_data_interval(
                timezone.coerce_datetime(last_automated_dagrun)
            )
        else:
            data_interval = last_automated_dagrun
        if restricted:
            restriction = self._time_restriction
        else:
            restriction = TimeRestriction(earliest=None, latest=None, catchup=True)
        try:
            info = self.timetable.next_dagrun_info(
                last_automated_data_interval=data_interval,
                restriction=restriction,
            )
        except Exception:
            self.log.exception(
                "Failed to fetch run info after data interval %s for DAG %r",
                data_interval,
                self.dag_id,
            )
            info = None
        return info
    def next_dagrun_after_date(self, date_last_automated_dagrun: Optional[pendulum.DateTime]):