`JobRepository#getJobNames()` always returns empty list

[kzander91]

Bug description
JobRepository#getJobNames() is not implemented by the only implementation of the interface, SimpleJobRepository. The default method simply returns an empty list.
As of Spring Batch 5, this method is used by JobRepositoryTestUtils.removeJobExecutions(), which became a no-op method, never removing any executions due to getJobNames() never returning any job names.

Environment
Spring Batch 5.0.0-RC2

Steps to reproduce

1. Run Job.
2. Call JobRepository.getJobNames().

Expected behavior
Names of jobs are returned.

Minimal Complete Reproducible example
demo1.zip

1. Unzip
2. Run mvnw spring-boot:run
3. The app runs a job named job and then queries both the batch_job_instance table and the JobRepository for all job names. The query returns job as expected, the JobRepository returns nothing.

[kzander91]

In fact, two other methods return empty lists as well due to not being implemented in SimpleJobRepository:

spring-batch/spring-batch-core/src/main/java/org/springframework/batch/core/repository/JobRepository.java

Lines 72 to 74 in 420a7ba

	default List<JobInstance> findJobInstancesByName(String jobName, int start, int count) {
	return Collections.emptyList();
	}

spring-batch/spring-batch-core/src/main/java/org/springframework/batch/core/repository/JobRepository.java

Lines 83 to 85 in 420a7ba

	default List<JobExecution> findJobExecutions(JobInstance jobInstance) {
	return Collections.emptyList();
	}

[fmbenhassine]

Good catch! I will plan the fix for 5.0 GA. Thank you for raising this 👍