### 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)

action="store_true",
)
ARG_POOL = Arg(("--pool",), "Resource pool to use")
ARG_DELAY_ON_LIMIT = Arg(
    ("--delay-on-limit",),
    help=(
        "Amount of time in seconds to wait when the limit "
        "on maximum active dag runs (max_active_runs) has "
        "been reached before trying to execute a dag run "
        "again"
    ),
    type=float,
    default=1.0,
)
ARG_RESET_DAG_RUN = Arg(
    ("--reset-dagruns",),
    help=(
        "if set, the backfill will delete existing "
        "backfill-related DAG runs and start "
        "anew with fresh, running DAG runs"
    ),
    action="store_true",
)
ARG_RERUN_FAILED_TASKS = Arg(
    ("--rerun-failed-tasks",),
    help=(
        "if set, the backfill will auto-rerun "
        "all the failed tasks for the backfill date range "
        "instead of throwing exceptions"
    ),