Replaces PowerReceiver's C# event with a ComponentMessage (#2888)

Co-authored-by: py01 <pyronetics01@gmail.com>

Content.Server/GameObjects/Components/Disposal/DisposalUnitComponent.cs

@@ -1,4 +1,4 @@
-#nullable enable
+#nullable enable
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -504,7 +504,7 @@ namespace Content.Server.GameObjects.Components.Disposal
             UpdateInterface();
         }
 
-        private void PowerStateChanged(object? sender, PowerStateEventArgs args)
+        private void PowerStateChanged(PowerChangedMessage args)
         {
             if (!args.Powered)
             {
@@ -574,11 +574,6 @@ namespace Content.Server.GameObjects.Components.Disposal
                 physics.AnchoredChanged += UpdateVisualState;
             }
 
-            if (Owner.TryGetComponent(out PowerReceiverComponent? receiver))
-            {
-                receiver.OnPowerStateChanged += PowerStateChanged;
-            }
-
             UpdateVisualState();
         }
 
@@ -589,11 +584,6 @@ namespace Content.Server.GameObjects.Components.Disposal
                 physics.AnchoredChanged -= UpdateVisualState;
             }
 
-            if (Owner.TryGetComponent(out PowerReceiverComponent? receiver))
-            {
-                receiver.OnPowerStateChanged -= PowerStateChanged;
-            }
-
             foreach (var entity in _container.ContainedEntities.ToArray())
             {
                 _container.ForceRemove(entity);
@@ -626,6 +616,10 @@ namespace Content.Server.GameObjects.Components.Disposal
                     _lastExitAttempt = _gameTiming.CurTime;
                     Remove(msg.Entity);
                     break;
+
+                case PowerChangedMessage powerChanged:
+                    PowerStateChanged(powerChanged);
+                    break;
             }
         }