### Description

After the release for Airflow 2.6.0 I was integrating some forms into our setup and was missing some options selections - and some nice features to make selections user friendly.

I'd like do contribute some few features into the user forms:
* A select box option where proposals are made but user is not limited to hard `enum` list (`enum` is restricting user input to only the options provided)
* A multi-option pick list (because sometimes a single selection is just not enough
* Labels so that technical values used to control the DAG are different from what is presented as option to user

### Use case/motivation

After the initial release of UI trigger forms, add more features (incrementially)

### Related issues

Relates or potentially has a conflict with #31299, so this should be merged before.

### 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)

ti: TaskInstance = kwargs["ti"]
        dag_run: DagRun = ti.dag_run
        if not dag_run.conf:
            print("Uups, no parameters supplied as DagRun.conf, was the trigger w/o form?")
            raise AirflowSkipException("No DagRun.conf parameters supplied.")
        print(f"This DAG was triggered with the following parameters:\n{json.dumps(dag_run.conf, indent=4)}")
    show_params()