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/Engines/Factions/Core/FactionSystem.cs

@@ -2,8 +2,9 @@ using System;
 
 namespace Server.Factions;
 
-public static class FactionSystem
+public class FactionSystem : GenericPersistence
 {
+    private static FactionSystem _factionSystem;
     public static bool Enabled { get; private set; }
 
     public static void Configure()
@@ -12,10 +13,14 @@ public static class FactionSystem
 
         if (Enabled)
         {
-            GenericPersistence.Register("Factions", Serialize, Deserialize);
+            _factionSystem = new();
         }
     }
 
+    public FactionSystem() : base("Factions", 10)
+    {
+    }
+
     // This does not do the actual work of removing faction stuff, only turns off the persistence.
     public static void Disable()
     {
@@ -24,7 +29,7 @@ public static class FactionSystem
             return;
         }
 
-        Persistence.Unregister("Factions");
+        _factionSystem.Unregister();
         Enabled = false;
         ServerConfiguration.SetSetting("factions.enabled", false);
     }
@@ -37,12 +42,12 @@ public static class FactionSystem
             return;
         }
 
-        GenericPersistence.Register("Factions", Serialize, Deserialize);
+        _factionSystem.Register();
         Enabled = true;
         ServerConfiguration.SetSetting("factions.enabled", true);
     }
 
-    private static void Serialize(IGenericWriter writer)
+    public override void Serialize(IGenericWriter writer)
     {
         writer.WriteEncodedInt(0); // version
 
@@ -59,7 +64,7 @@ public static class FactionSystem
         }
     }
 
-    private static void Deserialize(IGenericReader reader)
+    public override void Deserialize(IGenericReader reader)
     {
         var version = reader.ReadEncodedInt();