feat: Source generated Serialization/Deserialization (#550)

### Features
* Fully abstracts serialization by using compile-time attributes.
* Supports serializing the following:
  - Primitives (integers, strings, etc)
  - IP Addresses
  - BigDecimal
  - DateTime, Delta DateTimes
  - TimeSpan
  - Server.Race
  - Server.Map
  - Point2D, Point3D, Rect2D, Rect3D
  - Existing/New `ISerializable` references
  - Lists/Sets of serializable types
  - Type with a `Serialize` method and constructor that takes an `IGenericReader`
* Supports forward-only migration
* Supports existing RunUO deserialization for older versions by changing to the following signature:
  - `public void OldDeserialize(IGenericReader reader, int version)`
  - Must remove deserializing the version since this is already done
* Supports serializing from private fields or custom made properties.
* Types do not require inheriting Item/Mobile. Code gen will fully create `ISerializable` information.
  - This is not recommended yet, since it requires wiring to `Persistence` which will cause lots of unresolved symbol errors until code gen is built.

### Example
```cs
using System.Collections.Generic;

namespace Server.Items
{
    [Serializable(1)]
    public partial class TestItem1 : Item
    {
        [SerializableField(1)]
        [SerializableFieldAttr("[CommandProperty(AccessLevel.Administrator)]")]
        private List<Item> _someProperty;

        private void Deserialize(IGenericReader reader, int version)
        {
        }
    }
}
```

Generates this:
```cs
namespace Server.Items
{
    public partial class TestItem1
    {
#pragma warning disable 0414
        private const int _version = 1;
#pragma warning restore 0414

        [CommandProperty(AccessLevel.Administrator)]
        public System.Collections.Generic.List<Server.Item> SomeProperty
        {
            get => _someProperty;
            set
            {
                if (value != _someProperty)
                {
                    ((ISerializable)this).MarkDirty();
                    _someProperty = value;
                }
            }
        }

        public TestItem1(Serial serial) : base(serial)
        {
        }

        public override void Serialize(IGenericWriter writer)
        {
            var savePosition = ((Server.ISerializable)this).SavePosition;
            if (savePosition > -1)
            {
                writer.Seek(savePosition, System.IO.SeekOrigin.Begin);
                return;
            }
            writer.WriteEncodedInt(_version);
            writer.Write(_someProperty);
        }

        public override void Deserialize(IGenericReader reader)
        {
            var version = reader.ReadEncodedInt();
            if (version < 1)
            {
                OldDeserialize(reader, version);
                ((Server.ISerializable)this).MarkDirty();
                return;
            }
            SomeProperty = reader.ReadEntityList<Server.Item>();
        }
    }
}
```

And this:
```json
{
  "version": 1,
  "type": "TestItem1",
  "properties": [
    {
      "name": "SomeProperty",
      "type": "System.Collections.Generic.List\u003CServer.Item\u003E",
      "rule": "ListMigrationRule",
      "ruleArguments": [
        "Server.Item",
        "SerializableInterfaceMigrationRule"
      ]
    }
  ]
}
```

Projects/UOContent/Accounting/Account.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Net;
+using System.Runtime.CompilerServices;
 using System.Xml;
 using Server.Accounting.Security;
 using Server.Misc;
@@ -10,7 +12,7 @@ using Server.Network;
 
 namespace Server.Accounting
 {
-    public class Account : IAccount, IComparable<Account>
+    public partial class Account : IAccount, IComparable<Account>
     {
         public static readonly TimeSpan YoungDuration = TimeSpan.FromHours(40.0);
         public static readonly TimeSpan InactiveDuration = TimeSpan.FromDays(180.0);
@@ -23,7 +25,6 @@ namespace Server.Accounting
         private List<AccountTag> m_Tags;
         private TimeSpan m_TotalGameTime;
         private Timer m_YoungTimer;
-        private BufferWriter _saveBuffer;
 
         public Account(string username, string password) : this(Accounts.NewAccount)
         {
@@ -48,28 +49,13 @@ namespace Server.Accounting
         {
             Serial = serial;
 
-            var ourType = GetType();
-            TypeRef = Accounts.Types.IndexOf(ourType);
-
-            if (TypeRef == -1)
-            {
-                Accounts.Types.Add(ourType);
-                TypeRef = Accounts.Types.Count - 1;
-            }
+            SetTypeRef(GetType());
         }
 
         public Account(XmlElement node)
         {
             Serial = Accounts.NewAccount;
-
-            var ourType = GetType();
-            TypeRef = Accounts.Types.IndexOf(ourType);
-
-            if (TypeRef == -1)
-            {
-                Accounts.Types.Add(ourType);
-                TypeRef = Accounts.Types.Count - 1;
-            }
+            SetTypeRef(GetType());
 
             Username = Utility.GetText(node["username"], "empty");
 
@@ -141,6 +127,17 @@ namespace Server.Accounting
             Accounts.Add(this);
         }
 
+        public void SetTypeRef(Type type)
+        {
+            TypeRef = Accounts.Types.IndexOf(type);
+
+            if (TypeRef == -1)
+            {
+                Accounts.Types.Add(type);
+                TypeRef = Accounts.Types.Count - 1;
+            }
+        }
+
         /// <summary>
         ///     Object detailing information about the hardware of the last person to log into this account
         /// </summary>
@@ -270,11 +267,9 @@ namespace Server.Accounting
             }
         }
 
-        BufferWriter ISerializable.SaveBuffer
-        {
-            get => _saveBuffer;
-            set => _saveBuffer = value;
-        }
+        long ISerializable.SavePosition { get; set; }
+
+        BufferWriter ISerializable.SaveBuffer { get; set; }
 
         public int TypeRef { get; private set; }