Updates Message Packets (#321)

### API Breaking Change
Combined `AsciiMessage` and `UnicodeMessage` into a single function that takes two arguments, `bool ascii` and `string lang`. Lang can be null (or anything) if ascii is true. 

- [X] Changes message packets
- [X] Cleans up some code
- [X] Uses benchmarks to determine if the spanwriter + copyfrom

Projects/Benchmarks/Packets/BenchmarkPacketConstruction.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Buffers.Binary;
 using System.Collections.Generic;
 using BenchmarkDotNet.Attributes;
@@ -8,7 +9,7 @@ using Server.Network;
 
 namespace Benchmarks
 {
-    [MemoryDiagnoser, SimpleJob(RuntimeMoniker.NetCoreApp31)]
+    [SimpleJob(RuntimeMoniker.NetCoreApp50)]
     public class BenchmarkPacketConstruction
     {
         public List<BuyItemState> m_States;
@@ -150,7 +151,7 @@ namespace Benchmarks
                 w.Write((ushort)buyState.Hue);
             }
 
-            return w.Pos;
+            return w.Position;
         }
     }
 }