NoUI mode and Concurrency edits (#4092)

* Autorun changes

* Missed a handle

* Remove todo

---------

Co-authored-by: Chris Titus <dfm.titus@gmail.com>

functions/private/Hide-WPFInstallAppBusy.ps1

@@ -4,9 +4,9 @@ function Hide-WPFInstallAppBusy {
         Hides the busy overlay in the install app area of the WPF form.
         This is used to indicate that an install or uninstall has finished.
     #>
-    $sync.form.Dispatcher.Invoke([action]{
+    Invoke-WPFUIThread -ScriptBlock {
         $sync.InstallAppAreaOverlay.Visibility = [Windows.Visibility]::Collapsed
         $sync.InstallAppAreaBorder.IsEnabled = $true
         $sync.InstallAppAreaScrollViewer.Effect.Radius = 0
-    })
+    }
 }