`JobRepositoryTestUtils#removeJobExecutions()` Fails with Foreign Key Constraint Violation if Job Executions have Step Executions

[kzander91]

Related to #4229.

Bug description
Running a Job and then using JobRepositoryTestUtils#removeJobExecutions() fails, because the method does not delete the StepExecutions.
The method selects the executions to delete with this code:

spring-batch/spring-batch-test/src/main/java/org/springframework/batch/test/JobRepositoryTestUtils.java

Lines 168 to 171 in 9223826

	List<JobExecution> jobExecutions = this.jobRepository.findJobExecutions(jobInstance);
	if (jobExecutions != null && !jobExecutions.isEmpty()) {
	removeJobExecutions(jobExecutions);
	}

But findJobExecutions(JobInstance) does not populate the execution's stepExecutions attribute (we are missing a call to stepExecutionDao#addStepExecutions(JobExecution)):

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

Lines 100 to 103 in 9223826

	@Override
	public List<JobExecution> findJobExecutions(JobInstance jobInstance) {
	return this.jobExecutionDao.findJobExecutions(jobInstance);
	}

The subsequent call to removeJobExecutions(jobExecutions) then won't delete the StepExecutions, due to getStepExecutions() being empty:

spring-batch/spring-batch-test/src/main/java/org/springframework/batch/test/JobRepositoryTestUtils.java

Lines 148 to 151 in 9223826

	public void removeJobExecution(JobExecution jobExecution) {
	for (StepExecution stepExecution : jobExecution.getStepExecutions()) {
	this.jobRepository.deleteStepExecution(stepExecution);
	}

This causes FK constraint violations when the job executions themselves are then deleted afterwards.

Environment
Spring Batch 5.0.0-SNAPSHOT (this commit)

Steps to reproduce

1. Run a Job.
2. Call JobRepositoryTestUtils#removeJobExecutions()

Expected behavior
Method call succeeds, all executions are deleted.