add edge rendering for app dir for Turbopack (#50830)
### What?
* allow to use `runtime = "edge"` for app dir in turbopack
* move common imports from next-app-loader to
`packages/next/src/server/app-render/entry-base.ts`
* move common turbopack code to communicate between JS and Rust into
separate files
### Why?
A lot test cases depend on edge rendering
### How?
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Co-authored-by: Alex Kirszenberg <alex.kirszenberg@vercel.com>
