Collection selector function de-scopes the collection

[wwilsman]

An undocumented feature of the collection helper is its ability to generate a selector given a function. This is actually a feature of all interactors, and collection is able to utilize it since it returns a function whose arguments can be curried to the selector function.

radios = collection(value => `[type="radio"][value="${value}"]`);

interactor.radios('red') //=> scoped interactor for the red radio button.

However, new top-level Interactor instances are globally scoped which means that when collection encounters a function and passes it along to the constructor, that collection item becomes globally scoped.

Collections are meant to remain scoped, so we need to make it so passing a selector function retains that scope. After this work I think we can finally document this feature.