### 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)

default=None,
)
ARG_DAG_ID_REQ_FLAG = Arg(
    ("-d", "--dag-id"), required=True, help="The id of the dag"
)  
ARG_NO_BACKFILL = Arg(
    ("--no-backfill",), help="filter all the backfill dagruns given the dag id", action="store_true"
)
dagrun_states = tuple(state.value for state in DagRunState)
ARG_DR_STATE = Arg(
    ("--state",),
    help="Only list the DAG runs corresponding to the state",
    metavar=", ".join(dagrun_states),
    choices=dagrun_states,
)
ARG_DAG_ID_OPT = Arg(("-d", "--dag-id"), help="The id of the dag")
ARG_LIMIT = Arg(("--limit",), help="Return a limited number of records")
job_states = tuple(state.value for state in JobState)
ARG_JOB_STATE = Arg(
    ("--state",),
    help="Only list the jobs corresponding to the state",
    metavar=", ".join(job_states),
    choices=job_states,
)
ARG_NUM_EXECUTIONS = Arg(
    ("-n", "--num-executions"),
    default=1,
    type=positive_int(allow_zero=False),
    help="The number of next execution datetimes to show",
)