fix app router prefetch deduping (#68642)
The `Link` component has built in prefetch deduping behavior that was
added for pages router, since pages only supports a single kind of
prefetch.
Both pages & app routers share the `Link` component, meaning the
deduping behavior was enabled for both. However, app router supports
different [prefetch
types](https://nextjs.org/docs/app/api-reference/components/link#prefetch).
This means that if a page contains a link to a URL with auto
prefetching, followed by a URL with `prefetch={true}`, the full prefetch
would not be applied because it was short-circuited by `Link`.
Closes NDX-124
