First because there's no reason not to (we're not testing the behavior
for unmapped attributes), and second to work around a bug in Hibernate
ORM 7.0 alphas/betas: https://hibernate.atlassian.net/browse/HHH-18662

…ersistenceProvider

Not strictly necessary, but doesn't hurt and might allow more changes in
the next commits.

Because:

1. We currently disallow this for identifier generators only
   through a custom initializer for the identifier generator
   factory service, but that service is disappearing in Hibernate
   ORM 7.0.0.Beta1, leaving us only the setting `hibernate.cdi.extensions`.
   to disallow CDI for identifier generators -- and anything else
   that impacts metadata creation.
2. This is needed for quarkusio#40897,
   which will move more of metadata creation to build time -- where CDI
   is just not available.
3. Implementations of affected components needing access to CDI at
   runtime (so not during metadata creation) can still do so by
   calling `Arc.container()` to retrieve the relevant beans.

…equired dependencies

With Derby moving to hibernate-community-dialects, Quarkus will need to
add this dependency automatically.