revert to using cjs for lambda

[Rich-Harris]

fixes #4933. I don't truly understand why this was failing, but reverting to cjs rather than esm seems to fix it. If it turns out that other apps need esm then we can expose it as a config option

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[Rich-Harris]

Ah, wait. The switch to esm wasn't a generic modernisation, it was to enable top-level await. I guess we do need the option.

I also wonder if we can skip the esbuild step for lambdas by using @vercel/nft to include the necessary node_modules rather than bundling them into a single file — it's possible that we could then have our cake and eat it.

[benmccann]

Vite is considering only supporting ESM output for 3.0. It'd be nice if we could make that work

[Rich-Harris]

Vite isn't involved in this part at all

[furudean]

Can we merge this now in favor of unblocking some folk seeing as #4969 might take some time?

[Rich-Harris]

yep, i was hoping the nft version would work, but there are some lingering issues to work out