Collect metric coredns_build_info

```improvement user
An issue causing CoreDNS dashboard to show always 'No Data' is now fixed.
```

charts/seed-monitoring/charts/core/charts/prometheus/values.yaml

@@ -53,15 +53,16 @@ allowedMetrics:
   - container_network_receive_bytes_total
   - container_network_transmit_bytes_total
   coredns:
-  - process_max_fds
-  - process_open_fds
+  - coredns_build_info
   - coredns_cache_entries
   - coredns_cache_hits_total
   - coredns_cache_misses_total
   - coredns_dns_request_duration_seconds_count
   - coredns_dns_responses_total
   - coredns_forward_requests_total
   - coredns_forward_responses_total
+  - process_max_fds
+  - process_open_fds
   cloudControllerManager:
   - rest_client_requests_total
   - process_max_fds