Cleanup & Fixes for .NET 5 (#309)

- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet

Bumps release version

Projects/UOContent/Accounting/Security/MD5PasswordProtection.cs

@@ -22,7 +22,9 @@ namespace Server.Accounting.Security
     public class MD5PasswordProtection : IPasswordProtection
     {
         public static IPasswordProtection Instance = new MD5PasswordProtection();
+#pragma warning disable CA5351
         private readonly MD5CryptoServiceProvider m_MD5HashProvider = new MD5CryptoServiceProvider();
+#pragma warning restore CA5351
 
         public string EncryptPassword(string plainPassword)
         {