Make cleanup-leases security context configurable

[sirisaacnuketon]

Description of the change

The SecurityContext field for this job is currently static, however when deploying policy-controller into a namespace that uses Pod Security Admission controllers this job will not be able to run.

This adds a new field to the values file that operates in a manner similar to the securityContext option for the webhook deployment.

Existing or Associated Issue(s)

Additional Information

Checklist

• [x] Chart version bumped in Chart.yaml according to semver. Where applicable, update and bump the versions in any associated umbrella chart
• [x] Variables are documented in the values.yaml and added to the README.md. The helm-docs utility can be used to generate the necessary content. Use helm-docs --dry-run to preview the content.
• [x] JSON Schema generated.
• [x] List tests pass for Chart using the Chart Testing tool and the ct lint command.

[hectorj2f]

@sirisaacnuketon Please, could you fix the conflicts?