Metrics: Delete usage in services, finders, etc

Overview

⚠ Removal should take place during %16.0 or later.

⚠ Category:Metrics code is intertwined with the metrics GitLab reports on itself. Only Category:Metrics should be removed. Similarly, some items named like PrometheusAlert are also used for AlertManagement::Alert and should not be removed.

As part of Monitor: Metrics Deprecation and Removal (&10107 - closed), we want to remove all usages of the Metrics Dashboard part of Category:Metrics. This may be in services, finders, through model associations, etc. The models & data will be removed as part of Metrics: Delete models & database tables/columns (#397142 - closed).

Implementation plan

1. Delete all service classes made obsolete by:
   • Metrics: Delete API entrypoints & helpers (#397138 - closed)
   • Metrics: Delete GFM pipeline logic for embeds (#397137 - closed)
   • Metrics: Cleanup background workers & importers (#397141 - closed)
2. Delete relevant finder classes no longer in use
3. Find & remove any remaining usages of metrics dashboard models

Relevant code

The lists below are meant as an aid & may not be exhaustive.

Deletions:

• app/services/metrics/dashboard/\*
• app/services/prometheus/\*
• app/services/metrics/\*
• lib/gitlab/metrics/dashboard/\*
• config/prometheus/common_metrics.yml
• app/finders/metrics/*

Cleanups:

• app/models/environment.rb
• app/models/project.rb
• ee/app/services/dashboard/operations/list_service.rb
• app/models/integrations/prometheus.rb [Prometheus Alert Integrations use this as a data store, so we can't get rid of it entirely yet] also see https://gitlab.com/gitlab-org/gitlab/-/issues/409734
• app/policies/project_policy.rb
• ee/app/models/gitlab_subscriptions/features.rb