Improve `test-dev-server` and browser-based test infra

- [x] https://github.com/rolldown/rolldown/pull/7357
- [ ] To be discuss: Support test-only method `emitChnageFile`
- [x] test-dev-server support auto page reloading
- [ ] Use better way to support `@delay-transform` comment instead of using `setTimeout`
- [ ] Investigate why `editFile` need to wait/be async