[internal] Define rules to modularize packages in Next.js

From https://github.com/mui/material-ui/pull/35457#issuecomment-1676416983

we can scale this (modularizing the icons package) to all the MUI npm packages, beyond @mui/icons-material. It could be done with special rules, like in https://github.com/vercel/next.js/blob/261db496f7cf04b70f078a6eae0c8baf6fe5c238/packages/next/src/server/config.ts#L738. I didn't have time in https://github.com/vercel/next.js/pull/51953 to do it right, there was an urgency to fix it before it was rolled from their canary release to stable. Then, the question is is the Next.js job to keep this up to date? Is there a similar opportunity with Vite, should we update the Vite example as well? At the end of the day, it's about improving the DX.

Start with the linked MUI pull request discussion and the referenced Next.js packages/next/src/server/config.ts rule at line 738. Determine how package modularization rules should cover MUI npm packages, whether Next.js should maintain them, and whether the Vite example needs the same treatment. Done means the scope and ownership of those rules are defined.