Update Server Components documentation. (#40452)
This PR updates the server components documentation to make it more clear the benefit of server components and what their current status is inside Next.js.
It removes code snippets and CTAs for trying them out, as things have changed with the Layouts RFC since these docs were previously written. With the upcoming changes, server components will now be the default inside `app`. The list of supported and unsupported features was no longer accurate.
We will be providing more guidance as the layouts and routing changes are ready to be tested.
[Read the Layouts RFC](https://nextjs.org/blog/layouts-rfc) for more details.
