### 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)

ARG_SKIP_SERVE_LOGS,
        ),
    ),
    ActionCommand(
        name="dag-processor",
        help="Start a standalone Dag Processor instance",
        func=lazy_load_command("airflow.cli.commands.dag_processor_command.dag_processor"),
        args=(
            ARG_PID,
            ARG_DAEMON,
            ARG_SUBDIR,
            ARG_NUM_RUNS,
            ARG_DO_PICKLE,
            ARG_STDOUT,
            ARG_STDERR,
            ARG_LOG_FILE,
            ARG_VERBOSE,
        ),
    ),
    ActionCommand(
        name="version",
        help="Show the version",
        func=lazy_load_command("airflow.cli.commands.version_command.version"),
        args=(),
    ),
    ActionCommand(
        name="cheat-sheet",
        help="Display cheat sheet",
        func=lazy_load_command("airflow.cli.commands.cheat_sheet_command.cheat_sheet"),
        args=(ARG_VERBOSE,),