Remove IRelayMoveInput (#4663)

* Remove IRelayMoveInput

This interface gets called every time a movement key is pressed so it gets called a lot.

* Remove RelayMovementEntityMessage

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

Content.Shared/Movement/RelayMovementEntityEvent.cs

@@ -0,0 +1,14 @@
+using Robust.Shared.GameObjects;
+
+namespace Content.Shared.Movement
+{
+    public sealed class RelayMovementEntityEvent : EntityEventArgs
+    {
+        public IEntity Entity { get; }
+
+        public RelayMovementEntityEvent(IEntity entity)
+        {
+            Entity = entity;
+        }
+    }
+}