Separate destructible component threshold into behaviors (#2818)

* WIP changes, add behaviors

* Fix behavior typing, namespace and test

* NO SPACES

Content.Server/GameObjects/Components/Destructible/Thresholds/Behavior/IThresholdBehavior.cs

@@ -0,0 +1,11 @@
+using Content.Server.GameObjects.EntitySystems;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Interfaces.Serialization;
+
+namespace Content.Server.GameObjects.Components.Destructible.Thresholds.Behavior
+{
+    public interface IThresholdBehavior : IExposeData
+    {
+        void Trigger(IEntity owner, DestructibleSystem system);
+    }
+}