Add `maxsize` to available logrotate configs

Summary

Expose the maxsize for logrotate in the gitlab.rb configuration.

Proposal

Logrotate allows maxsize to be used together with frequency which makes it possible for users define a configuration that can rotate files based on the frequency but also able to rotate log files if they grow to the set maxsize.

References

https://linux.die.net/man/8/logrotate

https://gitlab.zendesk.com/agent/tickets/125746 (Internal Only)