feat: Covered Experience violations dashboard

Closes gitlab-com/gl-infra/observability/team#4165.

This MR introduces new recording rules to aggregate Covered Experience metrics, and an adapted version of the Application SLI Violations dashboard tailored for Covered Experiences.

Since this is a new dashboard, and the time series data to populated it depends on gitlab-com/gl-infra/observability/team#4261, there's no snapshot preview link to share yet.