Decouple AotRepositoryBuilder from type inspection.

[christophstrobl]

We should move the builder to operate upon a separate model feeded to it instead of mixing in type inspection. This helps decoupling building up the model from writing out the actual code.

Along the way we should make sure to remove code generation hooks from the builder as much as possible and limit access to javapoet API for implementing store modules.

This issue is basically a follow up to: #3339