unsafeToFutureCancelable's cancel future completes before setting the result future's cancellation status

The following fails fairly quickly:

while (true) {
  val (future, cancel) = IO.never.unsafeToFutureCancelable()
  Await.result(cancel(), Duration.Inf)
  assert(future.isCompleted)
}

I believe future actually has finished it's work, as the following doesn't fail:

while (true) {
  @volatile var started = false
  @volatile var done = false
  val io = IO { started = true }.bracket(_ => IO.never)(_ => IO { done = true })
  val (_, cancel) = io.unsafeToFutureCancelable()
  while (!started) {}
  Await.result(cancel(), Duration.Inf)
  assert(done)
}

This was mostly confusing in unit tests that were nondeterministic as they tested that the cancellation worked. I think it'd be more intuitive if the future's cancellation status was set before cancel completes, but maybe there's something else unintuitive that would result from that that I'm not considering.

Start by reproducing the two cancellation loops from the issue and inspect the unsafeToFutureCancelable entry point and its cancellation completion ordering. Compare when cancel() completes with when future.isCompleted becomes true; done should make the cancellation status observable before cancel() completes without breaking the demonstrated finalizer behavior.