Refactor drag and drop to use a shared interface (#2012)

* WIP in progress hours

* Cleanup

* Fix bugle

* Fix nullable error

* Merge fixes

* Merge fixes

* Merge fixes

Content.Shared/GameObjects/Components/SharedPlaceableSurfaceComponent.cs

@@ -1,9 +1,25 @@
+using System;
 using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
 
 namespace Content.Shared.GameObjects.Components
 {
     public abstract class SharedPlaceableSurfaceComponent : Component
     {
         public override string Name => "PlaceableSurface";
+        public override uint? NetID => ContentNetIDs.PLACEABLE_SURFACE;
+
+        public virtual bool IsPlaceable { get; set; }
+    }
+
+    [Serializable, NetSerializable]
+    public class PlaceableSurfaceComponentState : ComponentState
+    {
+        public readonly bool IsPlaceable;
+
+        public PlaceableSurfaceComponentState(bool placeable) : base(ContentNetIDs.PLACEABLE_SURFACE)
+        {
+            IsPlaceable = placeable;
+        }
     }
 }