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.Server/GameObjects/Components/Body/Behavior/StomachBehaviorComponent.cs

@@ -0,0 +1,24 @@
+using Content.Server.GameObjects.Components.Chemistry;
+using Content.Shared.GameObjects.Components.Body.Behavior;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Log;
+
+namespace Content.Server.GameObjects.Components.Body.Behavior
+{
+    [RegisterComponent]
+    [ComponentReference(typeof(SharedStomachBehaviorComponent))]
+    public class StomachBehaviorComponent : SharedStomachBehaviorComponent
+    {
+        protected override void Startup()
+        {
+            base.Startup();
+
+            if (!Owner.EnsureComponent(out SolutionContainerComponent solution))
+            {
+                Logger.Warning($"Entity {Owner} at {Owner.Transform.MapPosition} didn't have a {nameof(SolutionContainerComponent)}");
+            }
+
+            solution.MaxVolume = InitialMaxVolume;
+        }
+    }
+}