Investigate partial prerendering for layout routes

[remorses]

With Remix, you can create layouts using _layout.page.tsx routes, which are ideal for partial prerendering.

Partial prerendering consists in storing a parent component as an html file with some special syntax for "holes" that React can use to fill in with dynamic components.

Here is some example usage: https://github.com/facebook/react/blob/7771d3a7972cc2483c45fde51b7ec2d926cba097/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js#L6809

The use case would be improving SSR performance, right now if you use loaders you usually get pretty bad preformance because the full page needs to be rendered every time even if it does not change.

This feature would be similar to Astro server islands, which are dynamic components that are hydrated on a static page.

[remorses]

I know @jacob-ebey is researching the RSC implementation right now, it would be awesome to think about a prerendering implementation right now before the next Remix and react-router release