Remove IActionBlocker.CanMove (#4449)

* Remove IActionBlocker.CanMove

Ported the remainders over to using MovementAttemptEvent which should also help make mob movement a bit faster.

* Make that check faster

Content.Shared/Climbing/SharedClimbSystem.cs

@@ -0,0 +1,20 @@
+using Content.Shared.Movement;
+using Robust.Shared.GameObjects;
+
+namespace Content.Shared.Climbing
+{
+    public abstract class SharedClimbSystem : EntitySystem
+    {
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeLocalEvent<SharedClimbingComponent, MovementAttemptEvent>(HandleMoveAttempt);
+        }
+
+        private void HandleMoveAttempt(EntityUid uid, SharedClimbingComponent component, MovementAttemptEvent args)
+        {
+            if (component.OwnerIsTransitioning)
+                args.Cancel();
+        }
+    }
+}