detailed DNS request metrics

currently consul (server) is providing metrics for overall incoming DNS requests. It would be nice to have more detailed metrics, that would include counts for each service requests.

This would be extremely valuable in measuring service level metrics, related to response codes of requests from actual service nodes

Metrics could contain: service_id/service name or fqdn, DNS record type, time it took to respond, client IP.

Debug level log does have this information already.
Example from the log
`2020/11/18 22:15:37 [DEBUG] dns: request for name test.service.dc1.discovery.mydomain.com. type AAAA class IN (took 1.46234ms) from client 10.1.0.20:33068 (udp)
2020/11/18 22:15:39 [DEBUG] dns: request for name test.service.dc1.discovery.mydomain.com. type A class IN (took 1.635725ms) from client 10.1.0.20:36349 (udp)
2020/11/18 22:15:40 [DEBUG] dns: request for name test.service.dc1.discovery.mydomain.com. type A class IN (took 4.91848ms) from client 10.1.0.201:33464 (tcp)
2020/11/18 22:15:41 [DEBUG] dns: request for name test.service.dc1.discovery.mydomain.com. type A class IN (took 9.772059ms) from client 10.1.0.20:35081 (udp)
2020/11/18 22:15:41 [DEBUG] dns: request for name test.service.dc1.discovery.mydomain.com. type A class IN (took 8.44425ms) from client 10.1.0.20:33540 (tcp)`

at the moment we are using consul v1.3.1