Add destructible component threshold triggers (#3080)

* WIP changes

* Fix tests, merge conflict and trigger once behavior

* Update yml

* Change test strings to be consts

* Fix total damage types and classes triggers

* Simplify damage trigger logic, move state to Threshold

* Update outdated code and docs

* Change the name of IBehavior back to IThresholdBehavior

* Change human gibbing to trigger at 400 brute damage

* Change gibbing from brute to blunt damage

* Fix one (1) typo

* Add damage class trigger test

* Add missing nullable enable to thresholds

Content.Server/GameObjects/EntitySystems/DestructibleSystem.cs

@@ -11,8 +11,9 @@ namespace Content.Server.GameObjects.EntitySystems
     public class DestructibleSystem : EntitySystem
     {
         [Dependency] public readonly IRobustRandom Random = default!;
-        
+
         public AudioSystem AudioSystem { get; private set; }
+
         public ActSystem ActSystem { get; private set; }
 
         public override void Initialize()
@@ -23,4 +24,4 @@ namespace Content.Server.GameObjects.EntitySystems
             ActSystem = Get<ActSystem>();
         }
     }
-}
+}