feat(dataplane): allow token and tenancy information for proxied DNS

[DanStough]

Description

This is the Consul component of hashicorp/consul-dataplane#172

By passing along the tenant of the service being proxied we can more intelligently select the correct partition/namespace to use as defaults for DNS.

This also passes along the Consul ACL token as the x-consul-token grpc metadata. Eventually Consul should be able to use this token instead of the servers default token for authorizing access.

This PR also includes a small bit of cleanup as noted in the comments.

Testing & Reproduction steps

• Unit tests are updated

Links

Dataplane PR

PR Checklist

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