/model picker: type-to-filter

The modelPicker setting lets users add many models to the /model picker, for example one row per model from a gateway or router. With 60+ rows, the picker shows 10 at a time with "+54 models", and the only way to reach a row is to scroll.

Ask: let the user type to filter the list. Matching on label and model id is enough. Number keys, Enter and s would keep working on the filtered list.

Why it matters: a user with a gateway catalogue can type the model id (/model <id>), but the picker is the only place that shows which ids exist.

Optional: let plugin mods add a ModelPicker render component, so a mod can add its own filter.