fix: Cleans up entity persistence. Generalizes Mobiles/Items/Guilds (#1528)

### Summary
- [X] Fixed a bug where entity persistence was serialized out of order, causing world corruption.
- [X] Fixed LastSerialized not being utilized properly and dangling references still becoming an issue.
- [X] Added a new `GenericEntityPersistence<T>` type to encapsulate `ISerializable` serialization.
- [X] Removing the custom logic and moved Items, Mobiles, Guilds, and Accounts  to GenericEntityPersistence.
- [X] Changed serialization to use the singleton pattern to reduce calling methods from stored variables.

Projects/UOContent/Skills/AnimalTaming.cs

@@ -228,7 +228,7 @@ namespace Server.SkillHandlers
                     creature.AIObject?.DoMove(creature.Direction);
 
                     if (from is PlayerMobile pm &&
-                        !(pm.GetVirtues()?.HonorActive == true ||
+                        !(VirtueSystem.GetVirtues(pm)?.HonorActive == true ||
                           TransformationSpellHelper.UnderTransformation(pm, typeof(EtherealVoyageSpell))))
                     {
                         creature.Combatant = pm;