Allow the housekeeping tasks to be scheduled instead of executed on push
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### Description
We have several big repositories that get quite a lot of commits during the day, since the housekeeping lock the repository and are cpu intensive they can cause disruptions
### Proposal
Run the housekeeping tasks with cron so the user could schedule them to runn in out-of-office hours. There already is gitlab-ce#15021 which is similar however instead of disabling housekeeping for the project I'd rather just have it run when I don't need the repo.
issue