Drag changes (#2487)

* Drag changes

* Higlights only show near cursor
* Don't highlight un-droppable entities
* Fixes invalid highlights issue

* Also the scanner

* 2 months fix

* Address reviews

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Client/GameObjects/Components/Disposal/DisposalMailingUnitComponent.cs

@@ -1,4 +1,5 @@
 using Content.Shared.GameObjects.Components.Disposal;
+using Content.Shared.Interfaces.GameObjects.Components;
 using Robust.Shared.GameObjects;
 
 namespace Content.Client.GameObjects.Components.Disposal
@@ -7,5 +8,9 @@ namespace Content.Client.GameObjects.Components.Disposal
     [ComponentReference(typeof(SharedDisposalMailingUnitComponent))]
     public class DisposalMailingUnitComponent : SharedDisposalMailingUnitComponent
     {
+        public override bool DragDropOn(DragDropEventArgs eventArgs)
+        {
+            return false;
+        }
     }
 }