Data Layer replication bug

The bug is data layer runtime states can get out of sync between a client and a host depending on the initial runtime state of a data layer and the size of the replicated data layer names array.

See repro.

Repro:

• Add a data layer to a world. Set an initial runtime state of Activated or Loaded for the data layer.
• At some point in script (or code), change the data layer runtime state to Unloaded (could be on BeginPlay or later during the game).
• The Rep<Active|Loaded>DataLayerNames list on the host should now be empty.
• Add a client to the game. The client will not get an OnRep for RepActiveDataLayerNames or RepLoadedDataLayerNames if the array is empty on the host.
• The client now has a data layer in a different state from the host (because it initialized the data layer to the initial runtime state of Active or Loaded).
• If the host waits for the client to complete streaming (IsStreamingCompleted), it will never complete because the two are out of sync.

Reproduced this in UE5/main today (08/23/2024).