Define Heading levels in Settings App (#7496)

* Add shell page headings

* add headings for all the PTsettings

* add heading level 1 for the heading of each page

* Add heading level to the style instead of redifining it multiple times

* revert adding level2 for each control

* add heading level for run as admin because it does not follow the group style and rather the default style

src/core/Microsoft.PowerToys.Settings.UI/Views/GeneralPage.xaml

@@ -54,6 +54,7 @@
             <TextBlock x:Uid="Admin_Mode" 
                        FontWeight="SemiBold"
                        TextWrapping="Wrap"
+                       AutomationProperties.HeadingLevel="Level2"
                        Style="{StaticResource SubtitleTextBlockStyle}"/>
 
             <TextBlock Text="{x:Bind Mode=TwoWay, Path=ViewModel.RunningAsText}"