add CoreDNS nameserver check analyzer

Author: nvanthao

in-cluster/default.yaml

@@ -496,3 +496,15 @@ spec:
           - pass:
               when: "false"
               message: No OOMKilling event detected
+    - textAnalyze:
+        checkName: "CoreDNS nameserver configuration"
+        regex: "no nameservers found"
+        ignoreIfNoFiles: true
+        fileName: podlogs/coredns/coredns-*/coredns.log
+        outcomes:
+        - fail:
+            when: "true"
+            message: "CoreDNS reported missing nameserver configuration. Ensure /etc/resolv.conf has at least 1 'nameserver' configured"
+        - pass:
+            when: "false"
+            message: "CoreDNS found valid nameserver configuration"