Cherry-picking this from my work on the next-dev test runner.
This moves browser opening from the turbopack-dev-server crate into the next-dev crate, which has the cli entrypoint that runs the dev server. It looks like the dev server package is meant to be used as a library (it's only a library crate), and having this external side effect feels unexpected and makes it difficult to use this crate in situations like a test runner for next-dev, where we should test with a headless web browser.
Alternatively, opening the browser could be an option passed when creating the dev server, but this feels a bit cleaner to me.
Test Plan: `cargo run -p next-dev` and verify the browser still opens and successfully connects to the dev server.
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