add "overwrite mode" for the setup wizard, basically this just ignores the precondition of having whatever the page configures before showing it.

i.e. if you had keys installed, previously it'd skip right to firmware.

additionally added more customization to the now instance-based NotificationHelper

src/Ryujinx/UI/SetupWizard/SetupWizardPage.Builder.cs

@@ -48,7 +48,7 @@ namespace Ryujinx.Ava.UI.SetupWizard
             where TControl : RyujinxControl<TViewModel>, new()
             where TViewModel : SetupWizardPageContext, new()
         {
-            boundViewModel = new() { Notifications = ownerWizard.NotificationHelper };
+            boundViewModel = new() { Notifications = ownerWizard.Notification };
 
             return WithContent<TControl>(boundViewModel);
         }