feat(turbopack): add support for parallel routes and route intercepti…

…on (#57450)

### What?

We have to walk the directory tree recursively for every page (instead
of once) to get the correct loaderTree.

With this PR we walk the directory tree and for every
`page.(js,jsx,ts,tsx)` (entrypoint) we find we walk it again to get the
loader tree for that page


Closes WEB-1868
Closes WEB-1609