SlowContactsSystem to SpeedModifierContactsSystem mini rework (#26110)

* rework

* update logic

Content.Shared/Movement/Components/SpeedModifiedByContactComponent.cs

@@ -0,0 +1,12 @@
+using Robust.Shared.GameStates;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Movement.Components;
+
+/// <summary>
+/// Exists just to listen to a single event. What a life.
+/// </summary>
+[NetworkedComponent, RegisterComponent] // must be networked to properly predict adding & removal
+public sealed partial class SpeedModifiedByContactComponent : Component
+{
+}