Hide modules and types other than `prelude`

[moCello]

Summary

Hide all modules that don't need to be exposed outside of the crate.

Detailed Description

Technically we only want to expose the types from the prelude but at the moment we expose many more modules and their types. This leads to unnecessary breaking changes when we want to change the inner workings of plonk.
It might be though that downstream we are using types that are not included in the prelude yet. In that case we should consider adding those to the prelude and nonetheless hide the rest.