Change all of body system to use entities and components (#2074)

* Early commit

* Early commit 2

* merging master broke my git

* does anyone even read these

* life is fleeting

* it just works

* this time passing integration tests

* Remove hashset yaml serialization for now

* You got a license for those nullables?

* No examine, no context menu, part and mechanism parenting and visibility

* Fix wrong brain sprite state

* Removing layers was a mistake

* just tear body system a new one and see if it still breathes

* Remove redundant code

* Add that comment back

* Separate damage and body, component states, stomach rework

* Add containers for body parts

* Bring layers back pls

* Fix parts magically changing color

* Reimplement sprite layer visibility

* Fix tests

* Add leg test

* Active legs is gone

Crab rave

* Merge fixes, rename DamageState to CurrentState

* Remove IShowContextMenu and ICanExamine

Content.Client/GameObjects/Components/Body/Mechanism/MechanismComponent.cs

@@ -0,0 +1,34 @@
+#nullable enable
+using Content.Shared.GameObjects.Components.Body.Mechanism;
+using Content.Shared.GameObjects.Components.Body.Part;
+using Robust.Client.Interfaces.GameObjects.Components;
+using Robust.Shared.GameObjects;
+
+namespace Content.Client.GameObjects.Components.Body.Mechanism
+{
+    [RegisterComponent]
+    [ComponentReference(typeof(SharedMechanismComponent))]
+    [ComponentReference(typeof(IMechanism))]
+    public class MechanismComponent : SharedMechanismComponent
+    {
+        protected override void OnPartAdd(IBodyPart? old, IBodyPart current)
+        {
+            base.OnPartAdd(old, current);
+
+            if (Owner.TryGetComponent(out ISpriteComponent? sprite))
+            {
+                sprite.Visible = false;
+            }
+        }
+
+        protected override void OnPartRemove(IBodyPart old)
+        {
+            base.OnPartRemove(old);
+
+            if (Owner.TryGetComponent(out ISpriteComponent? sprite))
+            {
+                sprite.Visible = true;
+            }
+        }
+    }
+}