fix: Adds AfterSerialize support. Removes BeforeSerialize support. (#1208)

### Changes
* Implements an AfterSerialize method that is executed synchronously.
* Removes `BeforeSerialize` support since it was dangerous in its current implementation.
* Moves PlayerMobile kill/virtual decay to AfterSerialize.
* Adds kill decay to after Deserialize.

Projects/Server/IEntity.cs

@@ -103,10 +103,6 @@ public class Entity : IEntity
         && p.Y >= Location.m_Y - range
         && p.Y <= Location.m_Y + range;
 
-    public void BeforeSerialize()
-    {
-    }
-
     public void Deserialize(IGenericReader reader)
     {
         // Should not actually be saved
@@ -116,4 +112,10 @@ public class Entity : IEntity
     public void Serialize(IGenericWriter writer)
     {
     }
+
+    public bool ShouldExecuteAfterSerialize => false;
+
+    public void AfterSerialize()
+    {
+    }
 }