### 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)

"""Parses comma-separated list and returns list of string (strips whitespace)."""
    return [x.strip() for x in val.split(",")]
def string_lower_type(val):
    """Lowers arg."""
    if not val:
        return
    return val.strip().lower()
ARG_DAG_ID = Arg(("dag_id",), help="The id of the dag")
ARG_TASK_ID = Arg(("task_id",), help="The id of the task")
ARG_EXECUTION_DATE = Arg(("execution_date",), help="The execution date of the DAG", type=parsedate)
ARG_EXECUTION_DATE_OPTIONAL = Arg(
    ("execution_date",), nargs="?", help="The execution date of the DAG (optional)", type=parsedate
)
ARG_EXECUTION_DATE_OR_RUN_ID = Arg(
    ("execution_date_or_run_id",), help="The execution_date of the DAG or run_id of the DAGRun"
)
ARG_EXECUTION_DATE_OR_RUN_ID_OPTIONAL = Arg(
    ("execution_date_or_run_id",),
    nargs="?",
    help="The execution_date of the DAG or run_id of the DAGRun (optional)",
)
ARG_TASK_REGEX = Arg(
    ("-t", "--task-regex"), help="The regex to filter specific task_ids to backfill (optional)"
)
ARG_SUBDIR = Arg(
    ("-S", "--subdir"),
    help=(
        "File location or directory from which to look for the dag. "
        "Defaults to '[AIRFLOW_HOME]/dags' where [AIRFLOW_HOME] is the "