'utilities.ts' is an API surface hazard

`utilities.ts` consists of 4 different namespaces: * one which seems to be entirely internal * one which is entirely exposed * one which is entirely exposed *and* is entirely type predicate functions * one which is a random assortment of internal and exposed functions that have no consistent usage Just from my intuition and experience, I don't think this is a good idea. It's just too easy to put a new helper in some random section of the file and forget whether or not it's being exposed. As a naive first approximation, here's what I think would be more appropriate for each respective namespace: * `utilities.ts` * `publicUtilities.ts` * `publicPredicates.ts` * I don't know, TBD.