Add ability to specify cancellation propagation strategy when creating a Job/Deferred

[dovchinnikov]

I need a CompletableJob (and/or CompletableDeferred) such that:

• its parent propagates cancellation down to it;
• its parent waits for completion of it;
• it does not cancel its parent on failure regardless of whether a parent is a supervisor or not.

Currently this works, but it's ugly (pseudocode):

val intermediateSupervisor = SupervisorJob(parent = coroutineContext.job)
val child = Job(parent = intermediateSupervisor)
try {
  runWithChildAndCompleteIt(child) { ... }
}
finally {
  intermediateSupervisor.complete()
}

fun runWithChildAndCompleteIt(job: CompletableJob) {
  try {
  ...
    child.complete()
  }
  catch (t: Throwable) {
    child.completeExceptionally(t)
    throw t
  }
}