Add automation properties to expander-style settings (#13032)

## Summary of the Pull Request
Make sure we set `Name` and `FullDescription` on expander-style settings in the SUI

## PR Checklist
* [x] Closes #13019
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [x] I work here

## Validation Steps Performed
Accessibility insights now shows the name/full description for the expander-style settings

(cherry picked from commit 71cbdc8)
Service-Card-Id: 81446420
Service-Version: 1.13

src/cascadia/TerminalSettingsEditor/SettingContainer.cpp

@@ -122,28 +122,40 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 
         _UpdateOverrideSystem();
 
-        if (const auto& content{ Content() })
+        // Get the correct base to apply automation properties to
+        DependencyObject base{ nullptr };
+        if (const auto& child{ GetTemplateChild(L"Expander") })
+        {
+            if (const auto& expander{ child.try_as<Microsoft::UI::Xaml::Controls::Expander>() })
+            {
+                base = child;
+            }
+        }
+        else if (const auto& content{ Content() })
         {
             if (const auto& obj{ content.try_as<DependencyObject>() })
             {
-                // apply header text as name (automation property)
-                if (const auto& header{ Header() })
-                {
-                    const auto headerText{ header.try_as<hstring>() };
-                    if (headerText && !headerText->empty())
-                    {
-                        Automation::AutomationProperties::SetName(obj, *headerText);
-                    }
-                }
+                base = obj;
+            }
+        }
 
-                // apply help text as tooltip and full description (automation property)
-                const auto& helpText{ HelpText() };
-                if (!helpText.empty())
+        if (base)
+        {
+            // apply header as name (automation property)
+            if (const auto& header{ Header() })
+            {
+                if (const auto headerText{ header.try_as<hstring>() })
                 {
-                    Controls::ToolTipService::SetToolTip(obj, box_value(helpText));
-                    Automation::AutomationProperties::SetFullDescription(obj, helpText);
+                    Automation::AutomationProperties::SetName(base, *headerText);
                 }
             }
+
+            // apply help text as tooltip and full description (automation property)
+            if (const auto& helpText{ HelpText() }; !helpText.empty())
+            {
+                Controls::ToolTipService::SetToolTip(base, box_value(helpText));
+                Automation::AutomationProperties::SetFullDescription(base, helpText);
+            }
         }
 
         if (HelpText().empty())

src/cascadia/TerminalSettingsEditor/SettingContainerStyle.xaml

@@ -142,7 +142,8 @@
         <Setter Property="Template">
             <Setter.Value>
                 <ControlTemplate TargetType="local:SettingContainer">
-                    <muxc:Expander Margin="0,4,0,0"
+                    <muxc:Expander x:Name="Expander"
+                                   Margin="0,4,0,0"
                                    HorizontalAlignment="Stretch"
                                    HorizontalContentAlignment="Stretch"
                                    Content="{TemplateBinding Content}">