Scala's Futures constantly dip back into their ExecutionContext even when unnecessary; basically every single method on a Future causes it to go back to the Exe

Scala's Futures constantly dip back into their ExecutionContext even when unnecessary; basically every single method on a Future causes it to go back to the ExecutionContext. This means they can incur bookkeeping or at worst thread switching overhead for no good reason. For example, `map`ping over a completed Future has absolutely no need to go back to the ExecutionContext. Even `flatMap`ping multiple Futures together doesn't necessarily need an ExecutionContext if you offer a separate API to allow `Future`s to switch between threads (this also means that Futures must be delayed and can't run immediately). These are the big things that make things like ZIO and cats-effect IO faster (there are then other smaller things that differentiate those two from each other).