fix: Destroying player object removes observers.

[samlucas-unity]

Resolves issue when a player object is destroyed leaving the client connection intact - observers would be removed from network objects and not restored when a new player object is created for that client.

This issue affected 2.0.0 only.

fix: #3059

Changelog

• Fixed: Destroying the clients player object would cause it to be removed from NetworkObject observers list and wouldn't restore them when the player object was recreated. Fixes regression from 1.11.

Testing and Documentation

• Includes integration test PlayerSpawnNoObserversTest.SpawnDestoryRespawnPlayerObjectMaintainsObservers.
• No documentation changes or additions were necessary.