Compatibility artifact: Properly deprecate & point to new classes.

Better to start with a certain defined cluster of functionality, pick e.g. one of the following:

• field definitions,
• action definitions
• transformers, converters, validators etc

The ultimate goal is to have everything inside of compatibility artefact deprecated with a clear pointer to the non-deprecated counterpart. In case something appears to not have a clear replacement or even not a subject for deprecation at all, it has to be discussed on the case-by-case and the actions should be taken (follow-ups, extraction of the logic out of deprecated artefact etc).

Special consideration needs to be applied to deprecated code usage logic (info.magnolia.pages.rendering.registry.validator.DialogAwareTemplateDefinitionValidator and such). We need to provide a way to probably whitelist the definitions coming from compatibility artefact for the time being (for the sake of not polluting the definitions app with noise).