chore(vite): use different configs for admin and site; don't split assets into chunks

[marcelgerber]

I didn't want to go down this path necessarily, but:

• The splitting of our js/css into owid, common, admin is of dubious value, since there isn't much of an optimization since admin is used by very few people.
• In our bundlewatch checks, we sometimes have changes which move code from one bundle to the other; these always cause spurious bundlewatch errors then.
• But on the other hand, Vite/Rollup doesn't make it easy not to generate shared chunks between modules.
• ... so we need to resort to creating two Vite configs, and building both of them separately.

This fixes #2904.
It'll also probably speed up pageloads by a tiny bit.

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This doesn't change anything about the dev setup, which is still fully served by a single Vite dev server.
For production builds, we produce two types of outputs into two directories, /assets and /assets-admin:

These are now entirely self-contained and independent of each other.
This also means that the owid.mjs file no longer contains any import statements, which is what fixes #2904.

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TODOs

• Clean up manifest handling code
• Ensure admin works
• Ensure this works on staging servers
• Publish this to a staging CF Pages site: https://vite-separate-builds.owid-staging.pages.dev
• ... and test with Internet Archive: https://web.archive.org/web/20240403094959/https://vite-separate-builds.owid-staging.pages.dev/grapher/life-expectancy
• Check that embedCharts.js works
• Check that /assets-admin are properly served
• Split yarn buildVite into yarn buildViteAdmin and yarn buildViteSite
  • ...and skip /assets-admin build on owid-cloudflare-prod: Could save us 45 seconds for each code deploy...
• AFTER DEPLOY: do a ripgrep through the bakedSite directory and look for common.mjs

[marcelgerber]

Just confirmed that this actually fixes #2904:

This branch is deployed to https://vite-separate-builds.owid-staging.pages.dev/ on CF Pages (some thinks aren't loading correctly because the baseUrl was wrongly set - sorry for that...)

I then archived a grapher page on there: https://web.archive.org/web/20240403094959/https://vite-separate-builds.owid-staging.pages.dev/grapher/life-expectancy

And it works 🎉

[marcelgerber]

Main things to take care of (and which I've hopefully checked enough are):

• That /assets-admin is probably served on the admin
• That both types of assets are correctly copied to their respective places
• That VITE_PREVIEW=true mode works well
• That staging servers work well

[danyx23]

Amazing that you managed to find a solution for #2904! I think it would be best to talk this through with you and Ike and then I'll gladly play around with it. I'll send you a message to find a slot.

[danyx23]

Hi Marcel - unfortunately I didn't have time to check this anymore. Conceptually it's good but maybe it would be good if @ikesau could have a look at it before you merge it next week?