Backport of [NET-5217] [OSS] Derive sidecar proxy locality from parent service into release/1.16.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #18437 to be assessed for backporting due to the inclusion of the label backport/1.16.

🚨

Warning automatic cherry-pick of commits failed. If the first commit failed,
you will see a blank no-op commit below. If at least one commit succeeded, you
will see the cherry-picked commits up to, not including, the commit where
the merge conflict occurred.

The person who merged in the original PR is:
@zalimeni
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

merge conflict error: POST https://api.github.com/repos/hashicorp/consul/merges: 409 Merge conflict []

The below text is copied from the body of the original PR.

---

When registering sidecar proxies, ensure that locality is inherited from the parent service unless explicitly provided for the sidecar.

Also add logging to make inconsistencies between locality-aware routing policy and available locality data more obvious so that failover is not silently skipped unintentionally. (Enterprise-only)

Backporting only to 1.16.x since this feature was introduced in Consul 1.16.0.

Corresponding K8s PR: hashicorp/consul-k8s#2748

Description

• Inherit locality when registering sidecars
• Log warning when locality is missing with failover

Testing & Reproduction steps

• Added unit tests covering both changes in locality inheritance behavior

This creates the expected result when running enterprise int tests:

dd412229~static-server.default.dc1.internal.ea3f0006-415c-2bac-9779-321f3d10f883.consul=(*endpointv3.ClusterLoadAssignment)(0x40013608a0)(
cluster_name:"dd412229~static-server.default.dc1.internal.ea3f0006-415c-2bac-9779-321f3d10f883.consul" 
endpoints:{
  lb_endpoints:{
    endpoint:{
      address:{
        socket_address:{
          address:"172.17.0.3" 
          port_value:21001
        }
      }
    } 
    health_status:HEALTHY 
    load_balancing_weight:{
      value:1
    }
  }
} 
endpoints:{
  lb_endpoints:{
    endpoint:{
      address:{
        socket_address:{
          address:"172.17.0.3" 
          port_value:21002
        }
      }
    } 
    health_status:UNHEALTHY 
    load_balancing_weight:{
      value:1
    }
  } 
  priority:1
} 
endpoints:{
  lb_endpoints:{
    endpoint:{
      address:{
        socket_address:{
          address:"172.17.0.3" 
          port_value:21000
        }
      }
    } 
    health_status:HEALTHY 
    load_balancing_weight:{
      value:1
    }
  } 
  priority:2
})

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

---

Overview of commits

• b005940 - 1c1a015

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR

[hashicorp-cla]

All committers have signed the CLA.

[zalimeni]

The logging change portion (1 of 2 squashed commits) doesn't need to be backported to 1.16 due to the changes it targets not having been backported. The primary fix commit is retained here.