On the first frame, all startup scene objects are added to the physics scene.
This can cause a considerable delay, so we don't start raising the alarm on scene loop timeouts until the second frame.
This commit also slightly changes the behaviour of timeout reporting.
Previously, a report was made for the very first timed out thread, ignoring all others until the next watchdog check.
Instead, we now report every timed out thread, though we still only do this once no matter how long the timeout.
