Application setting for caching cleanup policy background jobs
Context
In #339129 (closed), we added caching for container registry cleanup policy background jobs. For GitLab.com this was incredibly useful to continue the rollout of the feature for all projects.
Problem to solve
The problem is self-managed instances may not want to use caching this way.
Proposal
Put the caching feature in an application setting. self-managed users can choose to not use caching at all.
Related to #339129 (closed).