Previously we restricted Float methods to only being callable while rendering. This allowed us to make associations between calls and their position in the DOM tree, for instance hoisting preinitialized styles into a ShadowRoot or an iframe Document.

When considering how we are going to support Flight support in Float however it became clear that this restriction would lead to compromises on the implementation because the Flight client does not execute within the context of a client render. We want to be able to disaptch Float directives coming from Flight as soon as possible and this requires being able to call them outside of render.

this patch modifies Float so that its methods are callable anywhere. The main consequence of this change is Float will always use the Document the renderer script is running within as the HoistableRoot. This means if you preinit as style inside a component render targeting a ShadowRoot the style will load in the ownerDocument not the ShadowRoot. Practially speaking it means that preinit is not useful inside ShadowRoots and iframes.

This tradeoff was deemed acceptable because these methods are optimistic, not critical. Additionally, the other methods, preconntect, prefetchDNS, and preload, are not impacted because they already operated at the level of the ownerDocument and really only interface with the Network cache layer.

When Float was first implemented the HostDispatcher was set and unset during each render. Now that we support dispatching globally the host extensions that did this Dispatcher shuffling is now a noop. Since these methods exist in all HostConfigs and they noop everywhere now we shoudl just remove them.