[Blazor] [Wasm] Improve prerendering support for applications with authentication

[javiercn]

• Design how an auth experience works across prerendering + spa sign in.
• Enable setting the user ahead of time during prerendering.
• Make sure that auth components can work correctly with prerendering.
• Add docs to make sure we offer proper guidance on how to architect the application to properly support prerendering.

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