Revert "Ensure _middleware is consistent in adapter for name/id" (#89624)
This is causing conflicts as the name value is relied on too much since
it can differ heavily e.g. for `src` dir and if not.
x-ref:
https://github.com/vercel/next.js/actions/runs/21767409431/job/62826336354#step:34:240
Reverts vercel/next.js#89559