This updates the fallback 404 handling to render the correct 404 page on the client when a 404 is returned from fetching the data route on a fallback page on the client. This prevents us from having to rely on a cache to be updated by the time we reload the page to prevent non-stop reloading. 

This also adds handling in serverless mode to ensure the correct 404 page is rendered when leveraging fallback: 'blocking' mode. 

Additional tests for the fallback: 'blocking' 404 handling will be added in a follow-up where returning notFound from `getServerSideProps` is also added.