[CE] feat(v2dns): add v2 style query metrics

[dhiaayachi]

Description

This PR adds metrics for the V2 DNS server per the RFC. The two V1 metrics are consolidated into "query" with a request type label. There are also some bugfixes to pre-register the staleness metric.

The new metric for queries is added to V1 so there is a migration path.

Testing & Reproduction steps

None really.

PR Checklist

• [ ] ~updated test coverage~
• [ ] ~external facing docs updated~ - This will happen in a separate PR
• [X] appropriate backport labels added
• [X] not a security concern

[dhiaayachi]

Thanks for the feature request! We appreciate your feedback and are always looking for ways to improve Consul.

At this time, Consul doesn't have V2 style query metrics. You can use Prometheus to track metrics for your Consul cluster, and then create custom metrics for your V2 DNS queries.