Clean up unused custom metrics frontend
What does this MR do and why?
Changes: This MR cleans up a portion of dead code related to the removal of devopsmonitor Category:Metrics features.
Scope: Everything under app/assets/javascripts/custom_metrics. This code was for the ability to add/remove/delete new project-based metrics in the UI. There are many other files to clean up still, but this should be a self-contained chunk.
Context: The Metrics Dashboard (used for monitoring apps deploying using gitlab) was deprecated in 14.7 and removed from the product in 16.0.
- grouprespond related issue: Metrics: Delete models & database tables/columns (#397142)
- Monitor:Metrics removal epic: Monitor: Metrics Deprecation and Removal (&10107)
- Reference MR with all related removals: Draft: Remove all remaining metrics dashboard-r... (!160325 - closed)
- Metrics removal is blocking cells: Drop old unused tables for prometheus alerts (#461838 - closed)
MR acceptance checklist
Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.
How to set up and validate locally
These features were disabled in %16.0 behind the :remove_monitor_metrics feature flag, and have been partially deleted since then. So there's nothing really to test here. It's no longer possible to set up these features.