fixes #44278

I wasn't sure if we should just add the tests to the hibernate-orm-jpamodelgen hence.. I kept the one in the new module as close to the hibernate-orm-jpamodelgen so that if we decide to merge them in that module, it'll be easier.

I've tested the config for the gradle doc example on a test project and this bit:
 annotationProcessor enforcedPlatform("${quarkusPlatformGroupId}:${quarkusPlatformArtifactId}:${quarkusPlatformVersion}")
 
seems to help with the version management for the AP in the Gradle case.

A quickstart draft PR is here: quarkusio/quarkus-quickstarts#1516