Add dev warning for cross-origin and stabilize allowedDevOrigins (#77044)
Adding a warning when we block cross-origin requests in dev so users are
aware this is why easier and know how to allow the origin through as
custom setups can use different origins and it be valid.
x-ref:
https://github.com/vercel/next.js/pull/76880#issuecomment-2718487112
---------
Co-authored-by: Jiachi Liu <inbox@huozhi.im>
Co-authored-by: Zack Tanner <1939140+ztanner@users.noreply.github.com>