Add healthcheck charts to Runway service dashboard

This MR adds health check probe details to the runway service dashboard.

See gitlab-com/gl-infra/platform/runway/team#165 (closed)

test_dashboard.sh generated dashboard does not seem to let me toggle the selectors so I've created one in the playground: https://dashboards.gitlab.net/d/runway-service-test/test-runway3a-runway-service-metrics?orgId=1&var-PROMETHEUS_DS=PA258B30F88C30650&var-environment=gprd&var-service=schin1-ai-assist-1579xx