Allow plugging in Hibernate ORM's `TypeContributor`, `FunctionContributor` and `AdditionalMappingContributor`

### Description

Those classes are the replacement for `MetadataBuilderContributor`, which is deprecated in Hibernate ORM 6.x.

### Implementation ideas

We could allow inserting these components through settings, `@PersistenceUnitExtension`, or both. See how it's done for `MetadataBuilderContributor` currently.