Non-optional OneToOne relation can't be lazy loaded anymore

I don't think it is an intended side effect, but with the fix for HHH-9460, which always sets the foreign key type to ForeignKeyDirection.TO_PARENT if the type references the primary key,
OneToOneType.isNullable() will return true, which then causes LoadEventListener.INTERNAL_LOAD_NULLABLE to be used rather than LoadEventListener.INTERNAL_LOAD_LAZY. This effectively prevents lazy loading to be used with non-optional/constrained OneToOne relations.

Testcase: https://github.com/hibernate/hibernate-orm/pull/2474