docs: update Next.js CLI docs (#62304)
## Description
It made sense to improve our <picture data-single-emoji=":nextjs:"
title=":nextjs:"><img class="emoji" width="20" height="auto"
src="https://emoji.slack-edge.com/T0CAQ00TU/nextjs/2a85d633ae594556.png"
alt=":nextjs:" align="absmiddle"></picture> CLI docs after refactoring
the CLI!
## Important Changes
- Removes mention of `next export`, which was moved to `next.config.js`
- Adds mention of `--turbo`
- Adds all the expected help outputs
## Related
- https://github.com/vercel/next.js/pull/61877
- Fixes https://github.com/vercel/next.js/issues/59226
Closes NEXT-2545
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Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>
Co-authored-by: Michael Novotny <manovotny@gmail.com>
Co-authored-by: Lee Robinson <me@leerob.io>
Co-authored-by: JJ Kasper <jj@jjsweb.site>
