HV-2031 Make PredefinedScopeHibernateValidatorFactory aware of constraint mappings defined purely in XML

[marko-bekhta]

https://hibernate.atlassian.net/browse/HV-2031

we have to:

• add the beans that are defined only in the XML (that's where beanClassesToInitialize.addAll( xmlMetaDataProvider.configuredBeanClasses() ) helps)
• make sure that the constraint helper has all the constraints we need. Initially it'll have the built-in ones for the ones requested by the config. But if the XML is trying to apply any other constraint, we will be in trouble, as the helper will not have the info. So to make it work the predefined factory is using a "dynamic" version of the helper that goes back to looking up the built-in constraints.

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