Add control namespaces to sample page header

[marcelwgn]

This PR adds the controls/APIs namespace to the top of the controls page:

Closes #1023

[gregwoo-microsoft]

The changes look great to me but I'm unable to load a control page for some reason. The app launches but when I try to click on a control, I get the "combase.pdb not loaded" error message. @chingucoding did you also get that error?

[marcelwgn]

I am not experiencing these issue @gregwoo-microsoft , that's really strange. If you could get a stack trace, it might be easier for me to see what could cause this.

[gregwoo-microsoft]

@chingucoding This is what I am getting. Let me know if this helps.

combase.dll!RoFailFastWithErrorContextInternal2(HRESULT hrError, unsigned long cStowedExceptions, _STOWED_EXCEPTION_INFORMATION_V2 * * aStowedExceptionPointers) Line 1471 C++
Microsoft.ui.xaml.dll!7b870d29() Unknown
Microsoft.ui.xaml.dll![Frames below may be incorrect and/or missing, no symbols loaded for Microsoft.ui.xaml.dll] Unknown
[External Code]
WinUIGallery.DesktopWap.dll!AppUIBasics.NavigationRootPage.EnsureNavigationSelection(string id) Line 214 C#
WinUIGallery.DesktopWap.dll!AppUIBasics.ItemPage.OnNavigatedTo(Microsoft.UI.Xaml.Navigation.NavigationEventArgs e) Line 191 C#
[External Code]
WinUIGallery.DesktopWap.dll!AppUIBasics.NavigationRootPage.Navigate(System.Type pageType, object targetPageArguments, Microsoft.UI.Xaml.Media.Animation.NavigationTransitionInfo navigationTransitionInfo) Line 180 C#
WinUIGallery.DesktopWap.dll!AppUIBasics.ItemsPageBase.OnItemGridViewItemClick(object sender, Microsoft.UI.Xaml.Controls.ItemClickEventArgs e) Line 71 C#
[External Code]

[marcelwgn]

@gregwoo-microsoft Could you try loading the symbols for Microsoft.UI.Xaml.dll? Maybe that helps tracking it down, looking at the stack trace, it seems that selecting an item is broken but that is not something that should be affected by this PR.

[marcelwgn]

@gregwoo-microsoft Is this good to go?

[gregwoo-microsoft]

Looks awesome! Thank you Marcel :)