feat: error code (#73332)
This update introduces a custom `swc-plugin` for Next.js that appends a
non-enumerable `__NEXT_ERROR_CODE` property to all `Error` instances,
enabling anonymous telemetry while keeping error codes hidden from
console logs. The plugin manages error codes through an append-only
`/packages/next/errors.json` file, which is automatically updated during
the `pnpm build` process using a two-pass system to ensure consistent
error mapping, even during concurrent builds.
