### 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.
("-n", "--num-executions"),
    default=1,
    type=positive_int(allow_zero=False),
    help="The number of next execution datetimes to show",
)
ARG_MARK_SUCCESS = Arg(
    ("-m", "--mark-success"), help="Mark jobs as succeeded without running them", action="store_true"
)
ARG_INCLUDE_DESCRIPTIONS = Arg(
    ("-d", "--include-descriptions"),
    help="Show descriptions for the configuration variables",
    action="store_true",
)
ARG_INCLUDE_EXAMPLES = Arg(
    ("-e", "--include-examples"), help="Show examples for the configuration variables", action="store_true"
)
ARG_INCLUDE_SOURCES = Arg(
    ("-s", "--include-sources"), help="Show source of the configuration variable", action="store_true"
)
ARG_INCLUDE_ENV_VARS = Arg(
    ("-V", "--include-env-vars"), help="Show environment variable for each option", action="store_true"
)
ARG_COMMENT_OUT_EVERYTHING = Arg(
    ("-c", "--comment-out-everything"),
    help="Comment out all configuration options. Useful as starting point for new installation",
    action="store_true",
)
ARG_EXCLUDE_PROVIDERS = Arg(
    ("-p", "--exclude-providers"),
    help="Exclude provider configuration (they are included by default)",