This PR introduces [Edge Runtime](https://edge-runtime.vercel.app/) for emulating [Edge Functions](https://vercel.com/features/edge-functions) locally.
Every time you run a [middleware](https://nextjs.org/docs/advanced-features/middleware) locally via `next dev`, an isolated edge runtime context will be created.
These contexts have the same constraints as production servers, plus they don't pollute the global scope; Instead, all the code run in a vm on top of a Node.js process.
Additionally, `@edge-runtime/jest-environment` has been added to make easier testing Edge Functions in a programmatic way.
It dropped the following polyfills from Next.js codebase, since they are now part of Edge Runtime:
- abort-controller
- formdata
- uuid
- web-crypto
- web-streams
Co-authored-by: Gal Schlezinger <2054772+Schniz@users.noreply.github.com>
