Refactor mind and ghost deletion code (#3680)

* Refactor mind and ghost deletion code

* Refactor to use EventBus and clean up deletes

* Fix mind eject when being deleted

* Refactor entity manager calls to use IEntity.EntityManager

Content.Server/GameObjects/Components/Mobs/VisitingMindComponent.cs

@@ -1,4 +1,5 @@
-using Content.Server.Mobs;
+#nullable enable
+using Content.Server.Mobs;
 using Robust.Shared.GameObjects;
 using Robust.Shared.ViewVariables;
 
@@ -18,4 +19,8 @@ namespace Content.Server.GameObjects.Components.Mobs
             Mind?.UnVisit();
         }
     }
+
+    public class MindUnvisitedMessage : EntityEventArgs
+    {
+    }
 }