Create metrics page, add stage ownership

Mark both the new operations/metrics page and the operations/ page
as belonging to Monitor.

doc/operations/index.md

+---
+stage: Monitor
+group: APM
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Project operations
 
 GitLab provides a variety of tools to help operate and maintain

doc/operations/metrics/index.md

+---
+stage: Monitor
+group: APM
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
+# Monitor CI/CD Environment metrics
+
+Once [configured](../../user/project/integrations/prometheus.md), GitLab will attempt to retrieve performance metrics for any
+environment which has had a successful deployment.
+
+GitLab will automatically scan the Prometheus server for metrics from known servers like Kubernetes and NGINX, and attempt to identify individual environments. The supported metrics and scan process is detailed in our [Prometheus Metrics Library documentation](../../user/project/integrations/prometheus_library/index.md).
+
+You can view the performance dashboard for an environment by [clicking on the monitoring button](../../ci/environments/index.md#monitoring-environments).
+
+## Metrics dashboard visibility
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/201924) in GitLab 13.0.
+
+You can set the visibility of the metrics dashboard to **Only Project Members**
+or **Everyone With Access**. When set to **Everyone with Access**, the metrics
+dashboard is visible to authenticated and non-authenticated users.

doc/user/project/integrations/prometheus.md

@@ -1270,14 +1270,6 @@ Prerequisites for embedding from a Grafana instance:
 1. In GitLab, paste the URL into a Markdown field and save. The chart will take a few moments to render.
    ![GitLab Rendered Grafana Panel](img/rendered_grafana_embed_v12_5.png)
 
-## Metrics dashboard visibility
-
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/201924) in GitLab 13.0.
-
-You can set the visibility of the metrics dashboard to **Only Project Members**
-or **Everyone With Access**. When set to **Everyone with Access**, the metrics
-dashboard is visible to authenticated and non-authenticated users.
-
 ## Troubleshooting
 
 When troubleshooting issues with a managed Prometheus app, it is often useful to