Add IEntity.IsWeightless extension method (#2255)

Checking manually every time wasn't that cool

Content.Shared/Physics/MoverController.cs

@@ -1,8 +1,6 @@
 #nullable enable
 using Content.Shared.GameObjects.Components.Movement;
 using Robust.Shared.GameObjects.Components;
-using Robust.Shared.Interfaces.Physics;
-using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 
@@ -10,14 +8,11 @@ namespace Content.Shared.Physics
 {
     public class MoverController : VirtualController
     {
-        [Dependency] private readonly IPhysicsManager _physicsManager = default!;
-
         public override IPhysicsComponent? ControlledComponent { protected get; set; }
 
         public void Move(Vector2 velocityDirection, float speed)
         {
-            if (ControlledComponent?.Owner.HasComponent<MovementIgnoreGravityComponent>() == false
-                && _physicsManager.IsWeightless(ControlledComponent.Owner.Transform.Coordinates))
+            if (ControlledComponent?.Owner.IsWeightless() ?? false)
             {
                 return;
             }