observability(runway): extend the artifact-registry overview with app KPIs
Adds an Application row to the generated artifact-registry-gke overview:
request rate by status class, p50/p99 request duration from the app histogram,
in-flight requests, handler panics, and a "Running build" stat reading
count by (version) (gitlab_artifact_registry_build_info) — more than one
value means a rolling deploy is in flight. The gauge ships since v1.477.0
(gitlab-org/ops/artifact-registry!2263 (merged)), so the panel renders live staging
data in the preview.
The generated overview only sees the service through runway_lb_*, so it shows
the load balancer's view of it. This row adds the app's own vantage. Panics and
in-flight requests exist only as app metrics, and the app series emit
continuously while the LB series are traffic-shaped, so the two rows do not go
quiet at the same time.
Modeled on dashboards/iam-data-gke-grpc/main.dashboard.jsonnet.
Preview: https://dashboards.gitlab.net/d/jpereira-verify-main