Tamland has GitLab.com specific parameters, which we generally like to push upstream to support https://gitlab.com/gitlab-com/gl-infra/scalability/-/issues/2273. Move outliers information from [`forecast_params.yml`](https://gitlab.com/gitlab-com/gl-infra/tamland/-/blob/main/forecast_params.yml) to the metrics catalog. This should work similar to how we represent changepoints: https://gitlab.com/gitlab-com/runbooks/-/merge_requests/6051