`use_root_id` hook

[Archmonger]

Current Situation

There is currently no convenient way to retrieve the id of the root component.

Proposed Actions

Create a use_root_id hook that fetches this value from the websocket or HTTP connection (pre-renders and regular renders). This is going to require building some additional infrastructure, since we currently only propagate the UUID to the component if it has template args/kwargs AND is using a websocket.