Add OwnerReference to generated Jobs

[ChristianCiach]

Since #486 Reloader is able to trigger Jobs from existing CronJob, which is awesome 🎉

But I noticed that the generated Jobs are missing owner references to the CronJob that was used to create them. This creates some issues:

• The created jobs are not deleted when the CronJob is deleted.
• The created jobs are not displayed in tools like ArgoCD or K9s.

Prior art:

• kubectl: https://github.com/kubernetes/kubectl/blob/5e1a193aef164bbd16b770684ff7711c6beed7d4/pkg/cmd/create/create_job.go#L268
• Kubernetes Dashboard: https://github.com/kubernetes/dashboard/blob/ee8b965861da0e6e6c3c764b91b7824f92383e15/modules/api/pkg/resource/cronjob/jobs.go#L121
• K9s: https://github.com/derailed/k9s/blob/39eef03373871388fc3cf2fa434d055e1eb97319/internal/dao/cronjob.go#L80
• ArgoCD: https://github.com/argoproj/argo-cd/blob/fe598a831e42a2838242f99d6a74be520f27908a/resource_customizations/batch/CronJob/actions/create-job/action.lua#L46

I successfully tested this change in one of our clusters.

[ChristianCiach]

I've added a commit that adds the annotation cronjob.kubernetes.io/instantiate: manual to jobs that have been triggered by Reloader. This seems to be a convention, because every other tool mentioned above (except for K9s) adds this annotation to manually scheduled jobs that have been created from cronjobs. I think this annotation is necessary to avoid a warning from the cronjob controller if it sees a job that has been created by another controller.