Clarify async scenarios and deadlocks

[adegeo]

Summary

A long time coming. Updates a few places with information about deadlocks and demonstrates code. Also adds reference to the new InvokeAsync methods in .NET 9.

Fixes #1406

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Internal previews

📄 File	🔗 Preview link
dotnet-desktop-guide/winforms/controls/how-to-make-thread-safe-calls.md	dotnet-desktop-guide/winforms/controls/how-to-make-thread-safe-calls
dotnet-desktop-guide/winforms/forms/events.md	dotnet-desktop-guide/winforms/forms/events

[KlausLoeffelmann]

Let's talk about a few aspects here.
We should also address .ConfigureAwait(true/false), and point out, how it can help in simplifying certain type of marshalling work, but can also impose deadlocks when applied poorly.

For the ValueTask issue in VB, I think I have a workaround, which we should provide in the docs.

[adegeo]

@KlausLoeffelmann I addressed your feedback.

• I also renamed snippets and code files to be clearer.
• I removed code that was unused.
• I also rewrote some of the snippets to better demonstrate the concepts being talked about here.
• One other thing I did was reorder the bullet points to emphasize InvokeAsync, then Invoke, then BackgroundWorker.

[BillWagner]

This looks really good @adegeo You can when ready.

[KlausLoeffelmann]

Couldn't agree more with @BillWagner.
Nicely done!
@merriemcgaw FYI.