better exception message for SerializableStateManager.GetStatefulGameObjectType

[andrew-raphael-lukasik]

What

More precise exception message for SerializableStateManager.GetStatefulGameObjectType method

Why

Misleading Exception: ISerializableGameObject type not implemented for DaggerfallWorkshop.Game.Serialization.SerializablePlayer appeared while working on #2442

Results

This PR does not resolve the underlying issue but fixes the messaging to clear out confusion first.

A new message is:

NotImplementedException: GetStatefulGameObjectType does not know what to do with DaggerfallWorkshop.Game.Serialization.SerializablePlayer
DaggerfallWorkshop.Game.Serialization.SerializableStateManager.GetStatefulGameObjectType (DaggerfallWorkshop.Game.Serialization.ISerializableGameObject sgObj) (at Assets/Scripts/Game/Serialization/SerializableStateManager.cs:495)
DaggerfallWorkshop.Game.Serialization.SerializableStateManager.DeregisterStatefulGameObject (DaggerfallWorkshop.Game.Serialization.ISerializableGameObject serializableObject) (at Assets/Scripts/Game/Serialization/SerializableStateManager.cs:263)
DaggerfallWorkshop.Game.Serialization.SaveLoadManager.DeregisterSerializableGameObject (DaggerfallWorkshop.Game.Serialization.ISerializableGameObject serializableObject) (at Assets/Scripts/Game/Serialization/SaveLoadManager.cs:553)
DaggerfallWorkshop.Game.Serialization.SerializablePlayer.OnDestroy () (at Assets/Scripts/Game/Serialization/SerializablePlayer.cs:88)

I am not familiar with this segment of the codebase atm to resolve this further on my own so I will leave that to the professionals to decide.

[Interkarma]

Thank you, I think this is a nice change. :)