improve `server-only` and `client-only` error message

[hi-ogawa]

We want to improve the following points:

• dev / build consistency
  • currently code frame is only shown during dev. (this is because resolveId error is caught by Vite import analysis's transform hook)
• it only shows the direct importer of xxx-only and that doesn't help much.

Maybe we can delay throwing errors from resolveId to later stage, perhaps buildEnd, so that we can check importer chains of xxx-only and improve error messages. (Improving the error message for build is more important than dev. Probably we cannot do much dev anyways.)

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It looks like sveltekit indeed checks their "server convention" during writeBundle. https://github.com/sveltejs/kit/blob/84298477a014ec471839adf7a4448d91bc7949e4/packages/kit/src/exports/vite/index.js#L516

Oh wait, the code actually changed now to use resolveId + load instead. sveltejs/kit#14155