Handle locales as Vite assets

[sandhose]

This makes it so that locales are handled as assets by Vite.

This has a few advantages:

• the assets names are hashed, so we can cache them
• we have an exhaustive list of all locales in the app
• so i18next can properly load the locales instead of trying a few
• we reduce bundle size because we have a simple custom loader instead of i18next-http-backend

Here's a diff of the JSON files being loaded with this patch:

[hughns]

This looks sane to me but I'm not familiar with the localazy setup. @fkwp could you sanity check this too?