Removed prometheus 1.8 config, new alerts and dashboards
Changes include:
- Removed Prometheus 1.8 configuration
- Updated Annotation & Gardener dashboards
- Updated gcp-service-discovery version to v1.3.1
- New alerts:
- Epoxy server is not online
- Nodes that fail to boot successfully
- Too many AppEngine versions
- Too many inactive AppEngine instances
- Updates to k8s dashboards