Fix pipeline with waskd2 experimental version (#44357)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
This pull request includes two main groups of changes: improvements to
build configuration (specifically, warning suppression for experimental
features), and refactoring in the `WrapPanelCustom` control to use the
correct `StretchChild` type from the CommunityToolkit. These updates
help streamline the build process and improve code clarity and
maintainability.

**Build configuration improvements:**

* Added `/p:IgnoreExperimentalWarnings=true` to the
`RestoreAdditionalProjectSourcesArg` in the build pipeline to enable
suppression of experimental warnings during project restore.
* Updated `Directory.Build.targets` to append specific warning codes
(`CS8305`, `SA1500`, `CA1852`) to the `NoWarn` property when
`IgnoreExperimentalWarnings` is set, suppressing these warnings during
builds.

**Refactoring in `WrapPanelCustom`:**

* Updated the `WrapPanel` control in `WrapPanel.cs` to use
`ToolkitStretchChild` from `CommunityToolkit.WinUI.Controls` instead of
a local `StretchChild` type, ensuring consistency and leveraging the
toolkit's implementation.
[[1]](diffhunk://#diff-53e4c6a2890b6fb1c66ea8a19f0049070910083608f8fb80c2b1f5a8d254d007R11-R12)
[[2]](diffhunk://#diff-53e4c6a2890b6fb1c66ea8a19f0049070910083608f8fb80c2b1f5a8d254d007L180-R184)
[[3]](diffhunk://#diff-53e4c6a2890b6fb1c66ea8a19f0049070910083608f8fb80c2b1f5a8d254d007L193-R197)
[[4]](diffhunk://#diff-53e4c6a2890b6fb1c66ea8a19f0049070910083608f8fb80c2b1f5a8d254d007L400-R402)
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## PR Checklist

- [ ] Closes: #xxx
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issues) -->
- [ ] **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

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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

.pipelines/v2/templates/job-build-project.yml

@@ -129,7 +129,7 @@ jobs:
       MSBuildMainBuildTargets: Build
     ${{ insert }}: ${{ parameters.variables }}
     ${{ if eq(parameters.useLatestWinAppSDK, true) }}:
-      RestoreAdditionalProjectSourcesArg: '/p:RestoreAdditionalProjectSources="$(Build.SourcesDirectory)\localpackages\NugetPackages"'
+      RestoreAdditionalProjectSourcesArg: '/p:RestoreAdditionalProjectSources="$(Build.SourcesDirectory)\localpackages\NugetPackages" /p:IgnoreExperimentalWarnings=true'
     ${{ else }}:
       RestoreAdditionalProjectSourcesArg: ''
   displayName: Build

Directory.Build.targets

@@ -24,4 +24,8 @@
 
     <MSBuild Projects="$(MSBuildProjectFullPath)" Targets="Restore" Properties="RestoreInProgress=true" BuildInParallel="false" />
   </Target>
+
+  <PropertyGroup Condition="'$(IgnoreExperimentalWarnings)' == 'true'">
+    <NoWarn>$(NoWarn);CS8305;SA1500;CA1852</NoWarn>
+  </PropertyGroup>
 </Project>

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/WrapPanelCustom/WrapPanel.cs

@@ -8,6 +8,8 @@ using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Windows.Foundation;
 
+using ToolkitStretchChild = CommunityToolkit.WinUI.Controls.StretchChild;
+
 namespace Microsoft.CmdPal.UI.Controls;
 
 /// <summary>
@@ -177,9 +179,9 @@ public sealed partial class WrapPanel : Panel
     /// <summary>
     /// Gets or sets a value indicating how to arrange child items
     /// </summary>
-    public StretchChild StretchChild
+    public ToolkitStretchChild StretchChild
     {
-        get { return (StretchChild)GetValue(StretchChildProperty); }
+        get { return (ToolkitStretchChild)GetValue(StretchChildProperty); }
         set { SetValue(StretchChildProperty, value); }
     }
 
@@ -190,9 +192,9 @@ public sealed partial class WrapPanel : Panel
     public static readonly DependencyProperty StretchChildProperty =
         DependencyProperty.Register(
             nameof(StretchChild),
-            typeof(StretchChild),
+            typeof(ToolkitStretchChild),
             typeof(WrapPanel),
-            new PropertyMetadata(StretchChild.None, LayoutPropertyChanged));
+            new PropertyMetadata(ToolkitStretchChild.None, LayoutPropertyChanged));
 
     /// <summary>
     /// Identifies the IsFullLine attached dependency property.
@@ -397,7 +399,7 @@ public sealed partial class WrapPanel : Panel
             Arrange(Children[i]);
         }
 
-        Arrange(Children[lastIndex], StretchChild == StretchChild.Last);
+        Arrange(Children[lastIndex], StretchChild == ToolkitStretchChild.Last);
 
         if (currentRow.ChildrenRects.Count > 0)
         {