Subtype Ternary enum

[schuler-henry]

Maybe we could subtype Ternary by reassigning Ternary.Always = true, Ternary.Never = false, Ternary.Maybe = Symbol('maybe') and have helper methods for the type to have helpers like toBool(maybeAs: boolean), alwaysOrMaybe(), onTernary<T>(tru: () => T, ...), and(a: Ternary, b: Ternary).

Originally posted by @EagleoutIce in #2321 (comment)