Rework behaviours to not reference elements outside of their behaviours to fix out of sync stuff with Hotwire Turbo

[Ambient-Impact]

In developing the Hotwire Turbo integration for the RefreshLess module, certain faulty assumptions have been revealed in various behaviours across our custom modules and the site theme; namely that we're relying on behaviours to find elements, store references to them, and then provide methods on the component to fetch those - this works fine most of the time if we only have to worry about full page loads, but this can break if a behaviour has been detached and a method is called to fetch an element, or if the method is called before a detach and the calling code stores a reference to that element, which will no longer exist in the DOM if Turbo has navigated to another page, and so on.

Solutions

The primary reason to have those methods on the components is that components are easy to reference from other code, but there's no single, easy way to reference specific elements in other code that it's expecting a component to provide.

One solution may be to finally rebuild everything using Stimulus, which may make it easier to properly contain and scope elements, but actually referencing elements directly is still a bit of an issue; they recommend using events to communicate between controllers, which may work, but further investigation is needed.