Simplify example infrastructure with Create(example) parameter

- Added bool example parameter to Application.Create()
- Added static ObservableCollection<IApplication> Apps for external observers
- When example=true, metadata is collected and demo keys are sent when first TopRunnable is modal
- Removed ExampleContextInjector complexity
- Examples now use Application.Create(example: isExample)
- Key injection happens via SessionBegun event monitoring TopRunnable.IsModal
- Clean, simple architecture that allows external observers to subscribe to Apps collection

This addresses @tig's feedback to simplify the approach.

Co-authored-by: tig <585482+tig@users.noreply.github.com>

Examples/Example/Example.cs

@@ -23,18 +23,16 @@ ConfigurationManager.Enable (ConfigLocations.All);
 // Check for test context to determine driver
 string? contextJson = Environment.GetEnvironmentVariable (ExampleContext.ENVIRONMENT_VARIABLE_NAME);
 string? driverName = null;
+var isExample = false;
 
 if (!string.IsNullOrEmpty (contextJson))
 {
     ExampleContext? context = ExampleContext.FromJson (contextJson);
     driverName = context?.DriverName;
+    isExample = true;
 }
 
-IApplication app = Application.Create ();
-
-// Setup automatic key injection for testing
-ExampleContextInjector.SetupAutomaticInjection (app);
-
+IApplication app = Application.Create (example: isExample);
 app.Init (driverName);
 app.Run<ExampleWindow> ();