### 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
DagRun.state == State.RUNNING,
                    DagRun.run_type != DagRunType.BACKFILL_JOB,
                    TaskInstance.state.in_(resettable_states),
                )
            ).all()
        else:
            resettable_tis = filter_by_dag_run.get_task_instances(state=resettable_states, session=session)
        tis_to_reset = [ti for ti in resettable_tis if ti.key not in queued_tis and ti.key not in running_tis]
        if not tis_to_reset:
            return 0
        def query(result, items):
            if not items:
                return result
            filter_for_tis = TaskInstance.filter_for_tis(items)
            reset_tis = (
                session.query(TaskInstance)
                .filter(filter_for_tis, TaskInstance.state.in_(resettable_states))
                .with_for_update()
                .all()
            )
            for ti in reset_tis:
                ti.state = State.NONE
                session.merge(ti)
            return result + reset_tis
        reset_tis = helpers.reduce_in_chunks(query, tis_to_reset, [], self.max_tis_per_query)
        task_instance_str = '\n\t'.join(repr(x) for x in reset_tis)
        session.flush()
        self.log.info("Reset the following %s TaskInstances:\n\t%s", len(reset_tis), task_instance_str)
        return len(reset_tis)