### Body

The CLI:

`airflow variables set [-h] [-j] [-v] key VALUE`

https://airflow.apache.org/docs/apache-airflow/stable/cli-and-env-variables-ref.html#set_repeat1

Doesn't support adding description though column exists and we support it from Rest API:
https://airflow.apache.org/docs/apache-airflow/stable/stable-rest-api-ref.html#operation/post_variables

**The Task:**

Allow to set description from cli command

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
ARG_TASK_REGEX,
            ARG_START_DATE,
            ARG_END_DATE,
            ARG_MARK_SUCCESS,
            ARG_LOCAL,
            ARG_DONOT_PICKLE,
            ARG_YES,
            ARG_CONTINUE_ON_FAILURES,
            ARG_DISABLE_RETRY,
            ARG_BF_IGNORE_DEPENDENCIES,
            ARG_BF_IGNORE_FIRST_DEPENDS_ON_PAST,
            ARG_SUBDIR,
            ARG_POOL,
            ARG_DELAY_ON_LIMIT,
            ARG_DRY_RUN,
            ARG_VERBOSE,
            ARG_CONF,
            ARG_RESET_DAG_RUN,
            ARG_RERUN_FAILED_TASKS,
            ARG_RUN_BACKWARDS,
            ARG_TREAT_DAG_AS_REGEX,
        ),
    ),
    ActionCommand(
        name="test",
        help="Execute one single DagRun",
        description=(
            "Execute one single DagRun for a given DAG and execution date.\n"
            "\n"
            "The --imgcat-dagrun option only works in iTerm.\n"