Changes required to unbreak vite-rolldown

[chen-anders]

Description 📖

This pull request contains changes to this plugin so that running vite with rolldown still works. I believe we're not inserting the correct entries into rolldownOptions causing us to run into this issue: vitejs/rolldown-vite#371

Background 📜

Since rolldown-vite expects rolldownOptions instead of rollupOptions and somehow both are present when the plugin in the current state is run, rollupOptions gets discarded, which means all the settings built up from the config function get dropped (e.g entrypoints)

The Fix 🔨

This fix detects whether we're using rolldown and sets the options appropriately. In addition, I attempted to fix an issue where outputFileName was being passed an undefined value , causing vite to fail building assets. Once I added if (typeof name === "undefined") return ""; - everything started building again.

[chen-anders]

It's not quite clear to me why my changes are causing test failures, but somehow all rails 7.2.x builds manage to pass 😓