### 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.
("file",),
    metavar="FILEPATH",
    help="Import pools from JSON file. Example format::\n"
    + textwrap.indent(
        textwrap.dedent(
            """
            {
                "pool_1": {"slots": 5, "description": "", "include_deferred": true},
                "pool_2": {"slots": 10, "description": "test", "include_deferred": false}
            }"""
        ),
        " " * 4,
    ),
)
ARG_POOL_EXPORT = Arg(("file",), metavar="FILEPATH", help="Export all pools to JSON file")
ARG_VAR = Arg(("key",), help="Variable key")
ARG_VAR_VALUE = Arg(("value",), metavar="VALUE", help="Variable value")
ARG_DEFAULT = Arg(
    ("-d", "--default"), metavar="VAL", default=None, help="Default value returned if variable does not exist"
)
ARG_DESERIALIZE_JSON = Arg(("-j", "--json"), help="Deserialize JSON variable", action="store_true")
ARG_SERIALIZE_JSON = Arg(("-j", "--json"), help="Serialize JSON variable", action="store_true")
ARG_VAR_IMPORT = Arg(("file",), help="Import variables from JSON file")
ARG_VAR_EXPORT = Arg(
    ("file",),
    help="Export all variables to JSON file",
    type=argparse.FileType("w", encoding="UTF-8"),
)
ARG_VAR_ACTION_ON_EXISTING_KEY = Arg(
    ("-a", "--action-on-existing-key"),