Fix weightlessness status effect appearing only after something checks if an entity is weightless (#2434)

* Revert "Add weightlessness status effect. (#2384)"

This reverts commit 9b751fc079.

* Bring back the icon and status

* Make weightless status track gravity and parent

Content.Shared/GameObjects/EntitySystemMessages/Gravity/GravityChangedMessage.cs

@@ -0,0 +1,17 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
+
+namespace Content.Shared.GameObjects.EntitySystemMessages.Gravity
+{
+    public class GravityChangedMessage : EntitySystemMessage
+    {
+        public GravityChangedMessage(IMapGrid grid)
+        {
+            Grid = grid;
+        }
+
+        public IMapGrid Grid { get; }
+
+        public bool HasGravity => Grid.HasGravity;
+    }
+}