Revise our AOT API surface as many methods have only a single usage within Commons and are not worth to be exposed. We also should reduce mutability and clarify the contracts for a clearer structuring of AOT contributions. Right now, parts are here and there. Introducing a AotRepositoryContextSupport for delegation to AotContext seems to be a good way to shield implementations from dropping future methods. Also, RepositoryRegistrationAotContribution and RepositoryRegistrationAotProcessor are super entangled and it makes sense to split both for a cleaner design.