Remove some BUI boilerplate (#28399)

* Remove some BUI boilerplate

- The disposals overrides got removed due to the helper method handling it.
- Replace window creation with CreateWindow helper.
- Fixed some stinky code which would cause exceptions.

* More

* moar

* weh

* done

* More BUIs

* More updates

* weh

* moar

* look who it is

* weh

* merge

* weh

* fixes

Content.Client/Gateway/UI/GatewayWindow.xaml.cs

@@ -22,7 +22,7 @@ public sealed partial class GatewayWindow : FancyWindow,
     public event Action<NetEntity>? OpenPortal;
     private List<GatewayDestinationData> _destinations = new();
 
-    public readonly NetEntity Owner;
+    public NetEntity Owner;
 
     private NetEntity? _current;
     private TimeSpan _nextReady;
@@ -46,16 +46,20 @@ public sealed partial class GatewayWindow : FancyWindow,
     /// </summary>
     private bool _isCooldownPending = true;
 
-    public GatewayWindow(NetEntity netEntity)
+    public GatewayWindow()
     {
         RobustXamlLoader.Load(this);
         var dependencies = IoCManager.Instance!;
         _timing = dependencies.Resolve<IGameTiming>();
-        Owner = netEntity;
 
         NextUnlockBar.ForegroundStyleBoxOverride = new StyleBoxFlat(Color.FromHex("#C74EBD"));
     }
 
+    public void SetEntity(NetEntity entity)
+    {
+
+    }
+
     public void UpdateState(GatewayBoundUserInterfaceState state)
     {
         _destinations = state.Destinations;