Refactor to support async streams

I'd love to support the library to use native reactive swift types so it doesn't have to depend on ReactiveSwift or require consumers to use ReactiveSwift

Start by mapping how KitUI's UIKit integration currently depends on ReactiveSwift; the issue names no files or tests, so the relevant entry points must first be located. Define the native reactive-stream scope and confirm that consumers can use KitUI without a ReactiveSwift dependency; the issue does not specify a concrete completion test.

Written by the indexing model from the issue text.