### 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_EMAIL_OPTIONAL = Arg(("-e", "--email"), help="Email of the user", type=str)
ARG_PASSWORD = Arg(
    ("-p", "--password"),
    help="Password of the user, required to create a user without --use-random-password",
    type=str,
)
ARG_USE_RANDOM_PASSWORD = Arg(
    ("--use-random-password",),
    help="Do not prompt for password. Use random string instead."
    " Required to create a user without --password ",
    default=False,
    action="store_true",
)
ARG_USER_IMPORT = Arg(
    ("import",),
    metavar="FILEPATH",
    help="Import users from JSON file. Example format::\n"
    + textwrap.indent(
        textwrap.dedent(
            """
            [
                {
                    "email": "foo@bar.org",
                    "firstname": "Jon",
                    "lastname": "Doe",
                    "roles": ["Public"],
                    "username": "jondoe"
                }
            ]"""
        ),