### 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.
"""Test variable_delete command"""
        variable_command.variables_set(self.parser.parse_args(["variables", "set", "foo", "bar"]))
        variable_command.variables_delete(self.parser.parse_args(["variables", "delete", "foo"]))
        with pytest.raises(KeyError):
            Variable.get("foo")
    def test_variables_import(self):
        """Test variables_import command"""
        with pytest.raises(SystemExit, match=r"Invalid variables file"):
            variable_command.variables_import(self.parser.parse_args(["variables", "import", os.devnull]))
    def test_variables_export(self):
        """Test variables_export command"""
        variable_command.variables_export(self.parser.parse_args(["variables", "export", os.devnull]))
    def test_variables_isolation(self, tmp_path):
        """Test isolation of variables"""
        path1 = tmp_path / "testfile1"
        path2 = tmp_path / "testfile2"
        
        variable_command.variables_set(self.parser.parse_args(["variables", "set", "foo", '{"foo":"bar"}']))
        variable_command.variables_set(self.parser.parse_args(["variables", "set", "bar", "original"]))
        variable_command.variables_export(self.parser.parse_args(["variables", "export", os.fspath(path1)]))
        variable_command.variables_set(self.parser.parse_args(["variables", "set", "bar", "updated"]))
        variable_command.variables_set(self.parser.parse_args(["variables", "set", "foo", '{"foo":"oops"}']))
        variable_command.variables_delete(self.parser.parse_args(["variables", "delete", "foo"]))
        variable_command.variables_import(self.parser.parse_args(["variables", "import", os.fspath(path1)]))
        assert "original" == Variable.get("bar")
        assert '{\n  "foo": "bar"\n}' == Variable.get("foo")
        
        variable_command.variables_export(self.parser.parse_args(["variables", "export", os.fspath(path2)]))
        assert path1.read_text() == path2.read_text()