Mark the coroutine started with UNDISPATCHED as running

[dkhalanskyjb]

This solves the issue of a coroutine started with CoroutineStart.UNDISPATCHED not being in the list of running coroutines when its code is, in fact, being executed.

It is still the case that several coroutines can be running on the same thread. For example, trying to run-to-cursor from "A" to "B" will actually enter the "B" in the outer coroutine in the following example:

suspend fun outer() {
  // run from here
  launch(start = CoroutineStart.UNDISPATCHED) {
    println("A")
    delay(1.seconds)
    target()
  }
  target()
}

suspend fun target() {
  println("B")
}

It's questionable whether this is incorrect; in any case, this is still less incorrect than what we have now, where the "B" in the inner coroutine would never get entered.

Fixes #4058

[qwwdfsad]

It's probably worth getting rid of this overload and use the one below, not a big fan of having test-only code in prod. Up to you