211433 metrics dashboard annotations reaper job worker

What does this MR do?

It adds two background jobs to implement #211433 (closed) metrics dashboard annotations retention feature. In this iteration we decided to not make cut off date configurable, but it wants to handle it in the future iteration

The retention policy of 14 days will eventually be configurable.

Underlying idea is to have one cron job only responsible for scheduling jobs with different cut off dates, that will come in handy especially when we will be adding possibility to customize cut off. And the second job which cycles and deletes in batches up to 10 000 records of annotations that extends cut off date.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content