observability: Fix and improve ET dashboards, not all of the common pods telemetry works for STSes

This commit fixes and/or improves parts of errortracking dashboards within GitLab Observability. Some of the panels specific to k8s deployments inherited via k8sPodsCommon do not work for the errortracking setup which are instead backed by statefulsets; this commit cleans them up, reformats query strings for better readability and adds a couple of metrics around versions/ready replicas.

Tested snapshot here: https://dashboards.gitlab.net/dashboard/snapshot/zJDYvHYS1Z4iwsX6X3vJGwqXOFG4WRhR?orgId=1