Auto-configure SimpleJobOperator with EnableBatchProcessing

[fmbenhassine]

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As of v4.3, @EnableBatchProcessing auto-configures all infrastructure beans except a JobOperator. So as a user, I still need to create a JobOperator bean myself like:

@Bean
public JobOperator jobOperator(JobLauncher jobLauncher, JobRegistry jobRegistry,
                               JobExplorer jobExplorer, JobRepository jobRepository) {
	SimpleJobOperator jobOperator = new SimpleJobOperator();
	jobOperator.setJobExplorer(jobExplorer);
	jobOperator.setJobLauncher(jobLauncher);
	jobOperator.setJobRegistry(jobRegistry);
	jobOperator.setJobRepository(jobRepository);
	return jobOperator;
}

Since all collaborators of the JobOperator (ie JobRepository, JobLauncher, JobRegistry, JobExplorer) are already created by @EnableBatchProcessing, this bean could also be created automatically by the annotation with those dependencies already set on it.