Bypass source map dev middleware for client chunks (#72581)
A multi-zone Next.js app might have complex rewrites for its client
assets. For these apps, resolving a source map through the
`/__nextjs_source-map` dev middleware might fail because the asset might
belong to a different app.
Instead of trying to resolve those rewrites (i.e. using `fetch` instead
of `fs`), we can just bypass the source map dev middleware for client
chunks. Because we control how those source maps are generated, we can
safely assume that the `sourceMappingURL` is relative to the filename,
with an added `.map` extension. The browser can just request this file,
and it gets served through the normal dev server, without the need to
route this through the source map dev middleware.
reverts #72258
