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/Items/Skill Items/Ninjitsu/LeatherNinjaBelt.cs

@@ -6,7 +6,7 @@ using Server.Mobiles;
 namespace Server.Items
 {
     [Flippable(0x2790, 0x27DB)]
-    public class LeatherNinjaBelt : BaseWaist, IDyable, INinjaWeapon
+    public class LeatherNinjaBelt : BaseWaist, INinjaWeapon
     {
         private Poison m_Poison;
         private int m_PoisonCharges;

Projects/UOContent/Items/Skill Items/Ninjitsu/NinjaWeapons.cs

@@ -39,7 +39,7 @@ namespace Server.Items
         void AttackAnimation(Mobile from, Mobile to);
     }
 
-    public class NinjaWeapon
+    public static class NinjaWeapon
     {
         private const int MaxUses = 10;