### 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)

"checked_number": Param(
            100,
            type="number",
            title="Number field with value check",
            description_html="""This field is required. You need to provide any number between 64 and 128.
            See the <a href='https://json-schema.org/understanding-json-schema/reference/numeric.html'>
            JSON schema description (numbers)</a> in for more details""",
            minimum=64,
            maximum=128,
            section="JSON Schema validation options",
        ),
        
        
        "object": Param(
            {"key": "value"},
            type=["object", "null"],
            title="JSON entry field",
            section="Special advanced stuff with form fields",
        ),
        
        
        
        "hidden_secret_field": Param("constant value", const="constant value"),
        
        
        "color_picker": Param(
            "#FF8800",
            type="string",
            title="Pick a color",
            description_html="""This is a special HTML widget as custom implementation in the DAG code.