Record feature category metrics for SLIs with a feature category

This adds a feature category recording with a static label for all SLIs that had a feature category defined.

The recordings are done separately from the key metrics to avoid duplication during a transition. This also means we don't need to adjust the anomaly detection alerts. The downside is that we're effectively evaluating the same rule twice but but recorded with different static labels

We're excluding the ones that had the feature category set to not_owned. Those recordings don't add a lot of value, and some services like Sidekiq and Puma might have their own feature category metrics.

Required for gitlab-com/gl-infra/scalability#967

This is an iteration of !3452 (merged) which was reverted in !3464 (merged)