Properly type edge handler fn (#86766)
Followup to https://github.com/vercel/next.js/issues/86765
There were quite a few cases where `page` wasn't actually passed to `adapter`. I hope I'm now passing the right string there.
The old `nHandler(opts: { page: string; request: RequestData }) was a lie, packages/next/src/server/web/sandbox/sandbox.ts` never passes `page`
