Fix mechanism events not being called properly, add test (#2279)

* Add mechanism events when added/removed to/from body/parts

* Change old usages

* Add TODO

* Remove BodyExtensions and IHasBody

* Remove unnecessary extensions and fix wrong event call in mechanism behavior component

* Complete test and fix event calls

Content.Server/GameObjects/Components/Body/SurgeryToolComponent.cs

@@ -68,7 +68,7 @@ namespace Content.Server.GameObjects.Components.Body
             _callbackCache = null;
 
             // Attempt surgery on a body by sending a list of operable parts for the client to choose from
-            if (eventArgs.Target.TryGetBody(out var body))
+            if (eventArgs.Target.TryGetComponent(out IBody? body))
             {
                 // Create dictionary to send to client (text to be shown : data sent back if selected)
                 var toSend = new Dictionary<string, int>();