Turbopack build: Fix type: module with output: standalone (#79292)
## What?
This PR ensures we first clean the `.next/standalone` folder before
writing into it.
Currently the order is:
1. Write package.json to `.next/standalone/package.json`
1. Delete `.next/standalone`
1. Check `.nft.json` files and write the files listed there to
`.next/standalone`
Which in turn causes the package.json to not exist.
So why does this not fail with webpack? Well, what I found is that the
`_app` `.nft.json` file somehow lists the project root `package.json`
even though it does not use it. This means that after we delete
`.next/standalone` the `package.json` will still end up in the eventual
directory regardless.
It fails with Turbopack because Turbopack correctly does not include the
package.json (as it's not used) and then the `package.json` is missing
at runtime, causing the `server.js` which uses ESM to fail (because the
detection for ESM is still valid regardless of deleting the folder).
New order is:
1. Delete `.next/standalone`
1. Write package.json to `.next/standalone/package.json`
1. Check `.nft.json` files and write the files listed there to
`.next/standalone`