Turn brain behavior into a component/system (#5281)

Content.Server/Body/Components/BrainComponent.cs

@@ -0,0 +1,12 @@
+using Content.Server.Body.Systems;
+using Robust.Shared.Analyzers;
+using Robust.Shared.GameObjects;
+
+namespace Content.Server.Body.Components
+{
+    [RegisterComponent, Friend(typeof(BrainSystem))]
+    public class BrainComponent : Component
+    {
+        public override string Name => "Brain";
+    }
+}