### 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
else:
                data_interval = dag.get_run_data_interval(run)
            orm_dag.calculate_dagrun_date_fields(dag, data_interval)
            for orm_tag in list(orm_dag.tags):
                if orm_tag.name not in set(dag.tags):
                    session.delete(orm_tag)
                    orm_dag.tags.remove(orm_tag)
            if dag.tags:
                orm_tag_names = [t.name for t in orm_dag.tags]
                for dag_tag in set(dag.tags):
                    if dag_tag not in orm_tag_names:
                        dag_tag_orm = DagTag(name=dag_tag, dag_id=dag.dag_id)
                        orm_dag.tags.append(dag_tag_orm)
                        session.add(dag_tag_orm)
        DagCode.bulk_sync_to_db(filelocs, session=session)
        
        
        session.flush()
        for dag in dags:
            cls.bulk_write_to_db(dag.subdags, session=session)
    @provide_session
    def sync_to_db(self, session=None):
        """
        Save attributes about this DAG to the DB. Note that this method
        can be called for both DAGs and SubDAGs. A SubDag is actually a
        SubDagOperator.
        :return: None
        """
        self.bulk_write_to_db([self], session)
    def get_default_view(self):