Add method getJobInstance in JobExplorer/JobRepository/JobOperator

[fmbenhassine]

As of v4.3.3, there is no way to get a job instance for a given job name + job parameters with a JobExplorer/JobRepository/JobOperator. This issue is to add a method getJobInstance(String jobName, JobParameters jobParameters) in JobRepository/JobExplorer/JobOperator.

[parikshitdutta]

Hi @benas, I am on it, please assign it to me.

Thank you.

[parikshitdutta]

Hi @benas, Please review submitted PR #3932. I will look forward to your feedback.

Thank you.