[CmdPal][UnitTests] Add/Migrate unit test for Apps and Bookmarks extension (#41238)

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fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
1. Create Apps and Bookmarks ut project.
2. Refactor Apps and Bookmarks. And some interface in these extensions
to add a abstraction layer for testing purpose.
New interface list:
* ISettingsInterface
* IUWPApplication
* IAppCache
* IBookmarkDataSource
3. Add/Migrate some test case for Apps and Bookmarks extension

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## PR Checklist

- [x] Closes: #41239 #41240
- [x] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **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

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

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---------

Co-authored-by: Yu Leng <yuleng@microsoft.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/AllAppsPage.cs

@@ -2,6 +2,7 @@
 // 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.Diagnostics;
 using System.Linq;
@@ -19,13 +20,20 @@ namespace Microsoft.CmdPal.Ext.Apps;
 public sealed partial class AllAppsPage : ListPage
 {
     private readonly Lock _listLock = new();
+    private readonly IAppCache _appCache;
 
     private AppItem[] allApps = [];
     private AppListItem[] unpinnedApps = [];
     private AppListItem[] pinnedApps = [];
 
     public AllAppsPage()
+        : this(AppCache.Instance.Value)
     {
+    }
+
+    public AllAppsPage(IAppCache appCache)
+    {
+        _appCache = appCache ?? throw new ArgumentNullException(nameof(appCache));
         this.Name = Resources.all_apps;
         this.Icon = Icons.AllAppsIcon;
         this.ShowDetails = true;
@@ -59,7 +67,7 @@ public sealed partial class AllAppsPage : ListPage
 
     private void BuildListItems()
     {
-        if (allApps.Length == 0 || AppCache.Instance.Value.ShouldReload())
+        if (allApps.Length == 0 || _appCache.ShouldReload())
         {
             lock (_listLock)
             {
@@ -75,7 +83,7 @@ public sealed partial class AllAppsPage : ListPage
 
                 this.IsLoading = false;
 
-                AppCache.Instance.Value.ResetReloadFlag();
+                _appCache.ResetReloadFlag();
 
                 stopwatch.Stop();
                 Logger.LogTrace($"{nameof(AllAppsPage)}.{nameof(BuildListItems)} took: {stopwatch.ElapsedMilliseconds} ms");
@@ -85,11 +93,11 @@ public sealed partial class AllAppsPage : ListPage
 
     private AppItem[] GetAllApps()
     {
-        var uwpResults = AppCache.Instance.Value.UWPs
+        var uwpResults = _appCache.UWPs
            .Where((application) => application.Enabled)
            .Select(app => app.ToAppItem());
 
-        var win32Results = AppCache.Instance.Value.Win32s
+        var win32Results = _appCache.Win32s
             .Where((application) => application.Enabled && application.Valid)
             .Select(app => app.ToAppItem());