Upgrade Hibernate ORM to 8.0

[DavideD]

See https://hibernate.org/orm/releases/8.0/

We need to start looking into this

[DavideD]

I guess Hibernate Reactive 5.0 is going to be Hibernate ORM 8.0 and Vert.x 4.5
and Hibernate Reactive 6.0 is going to be Hibernate ORM 8.0 and Vert.x 5.0.
But I will wait to create a new branch upstream until we have at least a POC