ZIO 1.0: Backport some improvements to supervisor

We can add these two new methods to ZIO 1.x `Supervisor` data type, with default, "do-nothing" implementations.

```scala
private[zio] def unsafeOnSuspend[E, A](fiber: Fiber.Runtime[E, A]): Unit
private[zio] def unsafeOnResume[E, A](fiber: Fiber.Runtime[E, A]): Unit
```

These methods must be called on fiber suspend / resume.

/cc @dkarlinsky 