Dependencies: Upgrade WinUIEx to 2.8.0 (#40639)

## Summary of the Pull Request

This change upgrades the WinUIEx NuGet package from version 2.2.0 to
2.8.0.
- Prevents the window itself from taking focus when it should not.
- Removes dead code from Settings.UI (the code triggered error
[WinUIEX1001](https://dotmorten.github.io/WinUIEx/rules/WinUIEx1001.html)
-- Window.Current is always null).
## PR Checklist

- [x] Closes: #40637
- [x] Closes: #7647
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

I've built and run [projects utilizing
WinUIEx](https://github.com/search?q=repo%3Amicrosoft%2FPowerToys+WinUIEx+path%3A*.*proj&type=code):
- Microsoft.CmdPal.UI
- MeasureToolUI
- FileLocksmithUI
- EnvironmentVariables
- AdvancedPaste
- Peek.UI
- RegistryPreview
- PowerToys.Settings
- Hosts

Directory.Packages.props

@@ -108,7 +108,7 @@
     <PackageVersion Include="UnicodeInformation" Version="2.6.0" />
     <PackageVersion Include="UnitsNet" Version="5.56.0" />
     <PackageVersion Include="UTF.Unknown" Version="2.6.0" />
-    <PackageVersion Include="WinUIEx" Version="2.2.0" />
+    <PackageVersion Include="WinUIEx" Version="2.8.0" />
     <PackageVersion Include="WPF-UI" Version="3.0.5" />
     <PackageVersion Include="WyHash" Version="1.0.5" />
     <PackageVersion Include="WixToolset.Heat" Version="5.0.2" />

src/settings-ui/Settings.UI/Activation/ActivationHandler.cs

@@ -1,44 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System.Diagnostics.CodeAnalysis;
-using System.Threading.Tasks;
-
-namespace Microsoft.PowerToys.Settings.UI.Activation
-{
-    // For more information on understanding and extending activation flow see
-    // https://github.com/Microsoft/WindowsTemplateStudio/blob/master/docs/activation.md
-    internal abstract class ActivationHandler
-    {
-        public abstract bool CanHandle(object args);
-
-        public abstract Task HandleAsync(object args);
-    }
-
-    [SuppressMessage("StyleCop.CSharp.MaintainabilityRules", "SA1402:File may only contain a single type", Justification = "abstract T and abstract")]
-    internal abstract class ActivationHandler<T> : ActivationHandler
-        where T : class
-    {
-        public override async Task HandleAsync(object args)
-        {
-            await HandleInternalAsync(args as T).ConfigureAwait(false);
-        }
-
-        public override bool CanHandle(object args)
-        {
-            // CanHandle checks the args is of type you have configured
-            return args is T && CanHandleInternal(args as T);
-        }
-
-        // Override this method to add the activation logic in your activation handler
-        protected abstract Task HandleInternalAsync(T args);
-
-        // You can override this method to add extra validation on activation args
-        // to determine if your ActivationHandler should handle this activation args
-        protected virtual bool CanHandleInternal(T args)
-        {
-            return true;
-        }
-    }
-}

src/settings-ui/Settings.UI/Activation/DefaultActivationHandler.cs

@@ -1,42 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-using System.Threading.Tasks;
-
-using Microsoft.PowerToys.Settings.UI.Services;
-using Windows.ApplicationModel.Activation;
-
-namespace Microsoft.PowerToys.Settings.UI.Activation
-{
-    internal sealed class DefaultActivationHandler : ActivationHandler<IActivatedEventArgs>
-    {
-        private readonly Type navElement;
-
-        public DefaultActivationHandler(Type navElement)
-        {
-            this.navElement = navElement;
-        }
-
-        protected override async Task HandleInternalAsync(IActivatedEventArgs args)
-        {
-            // When the navigation stack isn't restored, navigate to the first page and configure
-            // the new page by passing required information in the navigation parameter
-            object arguments = null;
-            if (args is LaunchActivatedEventArgs launchArgs)
-            {
-                arguments = launchArgs.Arguments;
-            }
-
-            NavigationService.Navigate(navElement, arguments);
-            await Task.CompletedTask.ConfigureAwait(false);
-        }
-
-        protected override bool CanHandleInternal(IActivatedEventArgs args)
-        {
-            // None of the ActivationHandlers has handled the app activation
-            return NavigationService.Frame.Content == null && navElement != null;
-        }
-    }
-}

src/settings-ui/Settings.UI/Services/ActivationService.cs

@@ -1,106 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
-
-using Microsoft.PowerToys.Settings.UI.Activation;
-using Microsoft.UI.Xaml;
-using Microsoft.UI.Xaml.Controls;
-using Windows.ApplicationModel.Activation;
-
-namespace Microsoft.PowerToys.Settings.UI.Services
-{
-    // For more information on understanding and extending activation flow see
-    // https://github.com/Microsoft/WindowsTemplateStudio/blob/master/docs/activation.md
-    internal sealed class ActivationService
-    {
-        private readonly App app;
-        private readonly Type defaultNavItem;
-        private Lazy<UIElement> shell;
-
-        private object lastActivationArgs;
-
-        public ActivationService(App app, Type defaultNavItem, Lazy<UIElement> shell = null)
-        {
-            this.app = app;
-            this.shell = shell;
-            this.defaultNavItem = defaultNavItem;
-        }
-
-        public async Task ActivateAsync(object activationArgs)
-        {
-            if (IsInteractive(activationArgs))
-            {
-                // Initialize services that you need before app activation
-                // take into account that the splash screen is shown while this code runs.
-                await InitializeAsync().ConfigureAwait(false);
-
-                // Do not repeat app initialization when the Window already has content,
-                // just ensure that the window is active
-                if (Window.Current.Content == null)
-                {
-                    // Create a Shell or Frame to act as the navigation context
-                    Window.Current.Content = shell?.Value ?? new Frame();
-                }
-            }
-
-            // Depending on activationArgs one of ActivationHandlers or DefaultActivationHandler
-            // will navigate to the first page
-            await HandleActivationAsync(activationArgs).ConfigureAwait(false);
-            lastActivationArgs = activationArgs;
-
-            if (IsInteractive(activationArgs))
-            {
-                // Ensure the current window is active
-                Window.Current.Activate();
-
-                // Tasks after activation
-                await StartupAsync().ConfigureAwait(false);
-            }
-        }
-
-        private static async Task InitializeAsync()
-        {
-            await Task.CompletedTask.ConfigureAwait(false);
-        }
-
-        private async Task HandleActivationAsync(object activationArgs)
-        {
-            var activationHandler = GetActivationHandlers()
-                                                .FirstOrDefault(h => h.CanHandle(activationArgs));
-
-            if (activationHandler != null)
-            {
-                await activationHandler.HandleAsync(activationArgs).ConfigureAwait(false);
-            }
-
-            if (IsInteractive(activationArgs))
-            {
-                var defaultHandler = new DefaultActivationHandler(defaultNavItem);
-                if (defaultHandler.CanHandle(activationArgs))
-                {
-                    await defaultHandler.HandleAsync(activationArgs).ConfigureAwait(false);
-                }
-            }
-        }
-
-        private static async Task StartupAsync()
-        {
-            await Task.CompletedTask.ConfigureAwait(false);
-        }
-
-        private static IEnumerable<ActivationHandler> GetActivationHandlers()
-        {
-            yield break;
-        }
-
-        private static bool IsInteractive(object args)
-        {
-            return args is IActivatedEventArgs;
-        }
-    }
-}

src/settings-ui/Settings.UI/Services/NavigationService.cs

@@ -24,12 +24,6 @@ namespace Microsoft.PowerToys.Settings.UI.Services
         {
             get
             {
-                if (frame == null)
-                {
-                    frame = Window.Current.Content as Frame;
-                    RegisterFrameEvents();
-                }
-
                 return frame;
             }