feat: Use Rolldown native MagicString

[timfish]

• Ref Prepare for rolldown/rolldown-vite usage #748

Once these features make it into a Rolldow release, it looks like the changes in this PR will improve sourcemap generation for Rolldown without affecting Rollup.

With an example app of 10k modules and 10MB output file:

	Time
Rolldown	900ms
Rolldown + Sentry Rollup plugin	4.5s
Rolldown + Sentry Rollup plugin + Combine injection plugins	1.8s
Rolldown + Sentry Rollup plugin + Combine injection plugins + native MagicString	1s

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

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New Features ✨

• Use Rolldown native MagicString by timfish in #846

Internal Changes 🔧

• (release) Fix changelog-preview permissions by BYK in #852

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[timfish]

This actually negates most of the overhead added by our plugin when using Rolldown!

It currently requires an experimental flag in the Rolldown config but I guess it will become the default eventually:

  experimental: {
    // Enable native Rust implementation of MagicString
    // This provides better performance for source map generation
    nativeMagicString: true,
  },

[logaretm]

Surprised to not see many changes here, nice one! Just a couple of questions/minor stuff

[logaretm]

q: could this check fail in the future since this is experimental? we could check meta.magicString again here instead. WDYT?

[timfish]

We only want to return { code: magicStringInstance as string } if this is a Rolldown native instance. The value of meta.magicString doesn't matter at this point.