Update Hibernate ORM package/class processing rules

fixes https://github.com/quarkusio/quarkus/issues/39299

I am not 100% sure about the changes in the first commit, but I'd expect that the package list should be explicit and not include subpackages. With the current behaviour DB objects for `other` PU in our tests were created by "accident" since the other pu did not explicitly define the properties to create them...