Make MapJobRegistry smart enough to auto register jobs defined in the application context

[fmbenhassine]

As of v5.2, it is required to populate the job registry with a different component (like a bean post processor, or smart initializing bean or something similar) before being able to use it with the JobOperator.

This feature request is to make the MapJobRegistry smart enough to auto register jobs defined in the application context. This would remove the need for a distinct component to populate the registry and therefore simplifies the configuration. While this could be done by creating a SmartMapJobRegistry that extends MapJobRegistry, I would keep things simple along the lines of #4847 and make MapJobRegistry itself a SmartInitializingSingleton.

Other jobs defined outside the application context could be registered manually by the user (same as before).