Add note on helper classes

[BillWagner]

Fixes #50695

For readers that want to build the app themselves, add notes about the necessary helper classes.

While here, do a freshness pass and update the sample version.

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Internal previews

📄 File	🔗 Preview link
docs/visual-basic/programming-guide/concepts/async/index.md	Asynchronous programming with Async and Await (Visual Basic)

[Copilot]

Pull request overview

This PR updates the Visual Basic async/await breakfast example so readers can identify (and copy) the helper “marker” types needed to compile the snippets, and it refreshes the sample metadata and target framework.

Changes:

• Add a dedicated HelperClasses snippet region to expose the missing Coffee, Egg, HashBrown, Toast, and Juice types.
• Add documentation guidance that points readers to those helper types when trying the sample code.
• Update the breakfast snippet project to target net10.0, and refresh the article ms.date.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
docs/visual-basic/programming-guide/concepts/async/snippets/breakfast/breakfast.vbproj	Bumps the sample project target framework to net10.0.
docs/visual-basic/programming-guide/concepts/async/snippets/breakfast/Program.vb	Adds snippet markers around helper types so they can be included in docs as a separate snippet.
docs/visual-basic/programming-guide/concepts/async/index.md	Adds a note and code include for the helper types, plus small editorial updates and refreshed metadata.