chore: use module-builder stub mode for more accurate types

[danielroe]

We added a prepare command for nuxt-module-build which allows creating type stubs directly from the module without needing to apply to the playground as well. (https://github.com/nuxt/module-builder/pull/124)

It's the default for new modules (https://github.com/nuxt/starter/pull/392).

This should allow us to match types more appropriately for module authors (for example, disallowing auto-imports) in future.