This change fixes an issue that can be reproduced when
a controller `onConnect` creates a `QueueTimeline` out
of the state of a legacy session and then `prepare` is called.
`activeQueueItemId`, `metadata` and the `queue` of the legacy
session are used when a `QueueTimeline` is created. The change
adds unit tests to cover the different combinatoric cases these
properties being set or unset.
PiperOrigin-RevId: 505731288
