The delegates are at the beginning for upgraded rooms and end for predecessors. Closes: network/neochat#620 and network/neochat#619
Make sure that the neochat can handle switching connection when the current one is logged out. This is mostly about using QPointer to handle use after free issues due to room objects being deleted.
Add delegate for showing the user a loading indicator and for the beginning of the timeline. BUG: 455045 BUG: 465285