refactor: subscription predicate

[neurosnap]

Motivation

This PR attempts to improve the performance of filtering streams by allowing a subscription to be called with a predicate. So instead of filtering on top of a stream (via filter()) we apply the filter logic within the stream. This makes it so when stream.send(...) gets called, the consumers only get activated if the item passes the predicate filter.

BEFORE

// create 100 consumers where 10 are listening for "action"
stream.send({ type: "action" });
// all 100 consumers get activated, but only 10 matching consumers continue their operation

AFTER

// create 100 consumers
stream.send({ type: "action" });
// only 10 consumers get activated and continue their operation