Expose minimal getClassOrder API without requiring __unstable__loadDesignSystem

[garrett-hopper]

The prettier-plugin-tailwindcss plugin currently depends on using __unstable__loadDesignSystem to get access to the getClassOrder API. This requires a bit of complex logic to define loadModule and loadStylesheet. (For v4 at least)

Ideally getClassOrder could be exposed by the tailwindcss package itself with minimal dependencies, using the same default loadModule and loadStylesheet logic as the normal build process.

My own interest comes from a VSCode extension I wrote to allow sorting of Tailwind classes in Clojure code, where the Prettier plugin would not have worked. (See tailwindcss-clojure-class-sorter/index.js#L113)

Having a dependable class sorting API beyond the Prettier plugin would be very useful in other contexts as well. There are a number of languages/syntaxes that can use tailwindcss-intellisense's tailwindCSS.experimental.classRegex option to get completion but are not able to benefit from the Prettier plugin for class sorting.