Seal/abstract/virtual everything (#6739)

Content.Shared/Stacks/SharedStackSystem.cs

@@ -123,7 +123,7 @@ namespace Content.Shared.Stacks
     /// <summary>
     ///     Event raised when a stack's count has changed.
     /// </summary>
-    public class StackCountChangedEvent : EntityEventArgs
+    public sealed class StackCountChangedEvent : EntityEventArgs
     {
         /// <summary>
         ///     The old stack count.

Content.Shared/Stacks/StackPrototype.cs

@@ -7,7 +7,7 @@ using Robust.Shared.ViewVariables;
 namespace Content.Shared.Stacks
 {
     [Prototype("stack")]
-    public class StackPrototype : IPrototype
+    public sealed class StackPrototype : IPrototype
     {
         [ViewVariables]
         [DataField("id", required: true)]