Refactoring body system to use containers and general body cleanup (#20202)

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Body/Organ/OrganComponent.cs

@@ -1,16 +1,16 @@
 using Content.Shared.Body.Systems;
+using Robust.Shared.Containers;
 using Robust.Shared.GameStates;
 
 namespace Content.Shared.Body.Organ;
 
-[RegisterComponent, NetworkedComponent]
+[RegisterComponent, NetworkedComponent, AutoGenerateComponentState]
 [Access(typeof(SharedBodySystem))]
 public sealed partial class OrganComponent : Component
 {
-    [DataField("body")]
+    /// <summary>
+    /// Relevant body this organ is attached to.
+    /// </summary>
+    [DataField("body"), AutoNetworkedField]
     public EntityUid? Body;
-
-    // TODO use containers. See comments in BodyPartComponent.
-    // Do not rely on this in client-side code.
-    public OrganSlot? ParentSlot;
 }