Composable views

Let us write views that can subscribe to other views.

For example you could have multiple views all internally subscribing to the same "entities in chunk x" base view, sharing its result set for a massive performance increase as opposed to resolving "entities in chunk x" in each view individually.

For a concrete example, all of these reducers could subscribe to "entities in chunk x" and then perform their own logic on top of the result set.
players_near_me
npcs_near_me
quest_givers_near_me
store_clerks_near_me
trees_near_me
ores_near_me
etc. etc. etc.