[Environment Variables] Using TitleBar (#41417)

Using `TitleBar` instead of our custom XAML.

No visual changes:

<img width="1254" height="216" alt="image"
src="https://github.com/user-attachments/assets/3e5bed64-3abe-421e-9345-59ad5228c134"
/>


- [X] Closes: #41414
- [ ] **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

src/modules/EnvironmentVariables/EnvironmentVariables/EnvironmentVariablesXAML/MainWindow.xaml

@@ -20,27 +20,14 @@
             <RowDefinition Height="Auto" />
             <RowDefinition Height="*" />
         </Grid.RowDefinitions>
-        <Grid
-            x:Name="titleBar"
-            Height="32"
-            ColumnSpacing="16">
-            <Grid.ColumnDefinitions>
-                <ColumnDefinition x:Name="LeftPaddingColumn" Width="0" />
-                <ColumnDefinition x:Name="IconColumn" Width="Auto" />
-                <ColumnDefinition x:Name="TitleColumn" Width="Auto" />
-                <ColumnDefinition x:Name="RightPaddingColumn" Width="0" />
-            </Grid.ColumnDefinitions>
-            <Image
-                Grid.Column="1"
-                Width="16"
-                Height="16"
-                VerticalAlignment="Center"
-                Source="../Assets/EnvironmentVariables/EnvironmentVariables.ico" />
-            <TextBlock
-                x:Name="AppTitleTextBlock"
-                Grid.Column="2"
-                VerticalAlignment="Center"
-                Style="{StaticResource CaptionTextBlockStyle}" />
-        </Grid>
+        <TitleBar x:Name="titleBar">
+            <!--  This is a workaround for https://github.com/microsoft/microsoft-ui-xaml/issues/10374, once fixed we should just be using IconSource  -->
+            <TitleBar.LeftHeader>
+                <ImageIcon
+                    Height="16"
+                    Margin="16,0,0,0"
+                    Source="/Assets/EnvironmentVariables/EnvironmentVariables.ico" />
+            </TitleBar.LeftHeader>
+        </TitleBar>
     </Grid>
 </winuiex:WindowEx>

src/modules/EnvironmentVariables/EnvironmentVariables/EnvironmentVariablesXAML/MainWindow.xaml.cs

@@ -4,22 +4,19 @@
 
 using System;
 using System.Runtime.InteropServices;
-
 using EnvironmentVariables.Win32;
 using EnvironmentVariablesUILib;
 using EnvironmentVariablesUILib.Helpers;
 using EnvironmentVariablesUILib.ViewModels;
 using ManagedCommon;
 using Microsoft.UI.Dispatching;
+using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using WinUIEx;
 
 namespace EnvironmentVariables
 {
-    /// <summary>
-    /// An empty window that can be used on its own or navigated to within a Frame.
-    /// </summary>
     public sealed partial class MainWindow : WindowEx
     {
         private EnvironmentVariablesMainPage MainPage { get; }
@@ -34,8 +31,9 @@ namespace EnvironmentVariables
             AppWindow.SetIcon("Assets/EnvironmentVariables/EnvironmentVariables.ico");
             var loader = ResourceLoaderInstance.ResourceLoader;
             var title = App.GetService<IElevationHelper>().IsElevated ? loader.GetString("WindowAdminTitle") : loader.GetString("WindowTitle");
+
             Title = title;
-            AppTitleTextBlock.Text = title;
+            titleBar.Title = title;
 
             var handle = this.GetWindowHandle();
             RegisterWindow(handle);