[next] support middleware-manifest v2

[nkzawa]

Related Issues

As the title, support a new version of middleware-manifest of next.js that is going to be added in vercel/next.js#39257

📋 Checklist

Tests

• The code changed/added as part of this PR has been covered with tests
• All tests pass locally with yarn test-unit

Code Review

• This PR has a concise title and thorough description useful to a reviewer
• Issue from task tracker has a link to this PR

[ijjk]

I'm seeing the below error while testing, we may want to clean up the error as it's not exactly clear which route was incorrect and the expected values.

21:55:12.935 | Created all serverless functions in: 46.001ms
21:55:12.967 | Collected static files (public/, static/, .next/static): 2.554ms
21:55:13.161 | Build Completed in /vercel/output [24s]
21:55:13.646 | Error: Mapping middleware not found. Maybe you provided a wrong middlewarePath? Available paths: middleware

[feugy]

Besides JJ's request for better error handling, no extra requests.

[nkzawa]

The error @ijjk mentioned should have already been fixed by https://github.com/vercel/api/pull/13624

[ijjk]

The changes here look good, will hold off on approving until the e2e deploy tests are passing on the Next.js PR though

[ijjk]

Thanks!