Add empty classes into the docs example (#29790)

* Remove note

In favor of updating the example along with the note.

* Add empty classes to Program.cs file

* Remove separate files for empty classes

* update example highlight to include additional empty classes and comment

Author: SeanKilleen

docs/csharp/programming-guide/concepts/async/index.md

@@ -25,15 +25,12 @@ For a parallel algorithm, you'd need multiple cooks (or threads). One would make
 
 Now, consider those same instructions written as C# statements:
 
-:::code language="csharp" source="snippets/index/AsyncBreakfast-starter/Program.cs" highlight="8-27":::
+:::code language="csharp" source="snippets/index/AsyncBreakfast-starter/Program.cs" highlight="8-34":::
 
 :::image type="content" source="media/synchronous-breakfast.png" alt-text="synchronous breakfast":::
 
 The synchronously prepared breakfast took roughly 30 minutes because the total is the sum of each task.
 
-> [!NOTE]
-> The `Coffee`, `Egg`, `Bacon`, `Toast`, and `Juice` classes are empty. They are simply marker classes for the purpose of demonstration, contain no properties, and serve no other purpose.
-
 Computers don't interpret those instructions the same way people do. The computer will block on each statement until the work is complete before moving on to the next statement. That creates an unsatisfying breakfast. The later tasks wouldn't be started until the earlier tasks had been completed. It would take much longer to create the breakfast, and some items would have gotten cold before being served.
 
 If you want the computer to execute the above instructions asynchronously, you must write asynchronous code.

docs/csharp/programming-guide/concepts/async/snippets/index/AsyncBreakfast-V2/Bacon.cs

@@ -6,6 +6,13 @@ namespace AsyncBreakfast
     class Program
     {
         // <SnippetMain>
+        // These classes are intentionally empty for the purpose of this example. They are simply marker classes for the purpose of demonstration, contain no properties, and serve no other purpose.
+        internal class Bacon { }
+        internal class Coffee { }
+        internal class Egg { }
+        internal class Juice { }
+        internal class Toast { }
+
         static async Task Main(string[] args)
         {
             Coffee cup = PourCoffee();