chore: Update gitaly dashboards to show decimal values for pack-object cache and remove ruby panel
What
- Add decimal values for pack-object cache
- Add panel for pack-object cache doc reference
- Remove ruby process metrics panel
Why
Looking at pack-object cache panels for low RPS gitaly servers, they show zero values which tend to be a bit confusing. Also, a handy reference to docs and current cache configs will be useful. Lastly, removed ruby process metrics panels as Gitaly servers are not running Ruby process anymore.
Reference issue: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/24656