build: Upgrade to Vite 5 (#2208)

[Vite 5 release notes](https://vitejs.dev/blog/announcing-vite5) look
like some possible performance gains. Another nice thing is aligning dev
and preview servers because I think the inconsistency caused annoying DX
when I tried to make embed-widget just a route in code-studio.

[Vite React
SWC](https://github.com/vitejs/vite-plugin-react-swc/releases). Main
thing is 3.7.0 supporting HMR for class components. Should be a nice
improvement for us.