Fix prerendered dynamic ISR functions for nested routes#900

This expands on the change in #834 and #864 to fix prerendered routes with nested routes (e.g. `[locale]/test/page.tsx` -> `nl/test` and `en/test`). I ran into an issue when adding localization with pre-rendered pages to my project on Cloudflare Pages. Everything generally worked, but dynamic routes with nested structures failed to build without `export const runtime = 'edge';`, which shouldn’t be required. This fix applies similar logic to handle nested dynamic ISR routes as with simple dynamic routes. This PR fixes #899, if you would like to use the changes immediately the package is released on [@rickmartensnl/next-on-pages](https://www.npmjs.com/package/@rickmartensnl/next-on-pages).