use ServiceMonitors to generate Prometheus Kubernetes config

manifests/prometheus/prometheus-k8s.yaml

@@ -1,11 +1,14 @@
 apiVersion: monitoring.coreos.com/v1alpha1
 kind: Prometheus
 metadata:
-  name: prometheus-k8s
+  name: k8s
   labels:
     prometheus: k8s
 spec:
-  version: v1.4.1
+  version: v1.5.2
+  serviceMonitorSelector:
+    matchExpression:
+    - {key: k8s-apps, operator: Exists}
   resources:
     requests:
       # 2Gi is default, but won't schedule if you don't have a node with >2Gi
@@ -13,3 +16,8 @@ spec:
       # production use. This value is mainly meant for demonstration/testing
       # purposes.
       memory: 400Mi
+  alerting:
+    alertmanagers:
+    - namespace: monitoring
+      name: alertmanager-main
+      port: web