### Description

Currently, the `airflow variables export` command requires an explicit file path and does not support output to stdout. However connections can be printed to stdout using `airflow connections export -`. This inconsistency between the two export commands can lead to confusion and limits the flexibility of the variables export command.

### Use case/motivation

To bring some consistency, similar to connections, variables should also be printed to STDOUT, using `-` instead of filename. 

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] 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)

"""Imports connections from a file."""
    if os.path.exists(args.file):
        _import_helper(args.file, args.overwrite)
    else:
        raise SystemExit("Missing connections file.")
def _import_helper(file_path: str, overwrite: bool) -> None:
    """Load connections from a file and save them to the DB.
    :param overwrite: Whether to skip or overwrite on collision.
    """
    connections_dict = load_connections_dict(file_path)
    with create_session() as session:
        for conn_id, conn in connections_dict.items():
            try:
                helpers.validate_key(conn_id, max_length=200)
            except Exception as e:
                print(f"Could not import connection. {e}")
                continue
            existing_conn_id = session.scalar(select(Connection.id).where(Connection.conn_id == conn_id))
            if existing_conn_id is not None:
                if not overwrite:
                    print(f"Could not import connection {conn_id}: connection already exists.")
                    continue
                
                conn.id = existing_conn_id
            session.merge(conn)
            session.commit()
            print(f"Imported connection {conn_id}")
@suppress_logs_and_warning
@providers_configuration_loaded
def connections_test(args) -> None: