Remove usage of JobFactory in JobRegistry

[fmbenhassine]

Along the lines of #4847 , this issue is to remove the usage of JobFactory from JobRegistry (and MapJobRegistry).

The API change is as follows:

-- void register(JobFactory jobFactory) throws DuplicateJobException;
++ void register(Job job) throws DuplicateJobException;

JobFactory is not a public (but not "user facing") API, but is still used in a user facing API. To simplify things, registering a job in a registry should not be done through a factory.