Do not re-render entire page for a single server component.

[mayank1513]

Goals

1. If you use cookies in any of the components, the entire page will become non-SSG (Update blog_starter to support dark mode #66794)
   a. Assuming same is true for server component fetching data with revalidation
2. What is the use of server components if the components which are not wrapped in server component also re-render when server component re-renders
3. Re-rendering of a server component should affect only that server component or its children and not the other components, i.e., site should be partially static → should not re-render on every request.

Non-Goals

Background

As evident in discussion over this PR - #66794, it would be great if we could sync the light/dark mode data with a single component on server side - to avoid FOUC.

This can be done by using cookies. However, this makes the entire page SSR. Only the component that requires cookies - may be along with its children - should re-render on each request and the sibling should be server as SSG.

Proposal

Yes. I am interested in contributing. However, I need some help in understanding the implementation of Sever Components and how and when they are rendered.