Lightweight consul agent

Nowadays especially in Kubernets based infrastructures there are some features that the consul agents/servers implements that imho are just a scalability burden in big consul installation (2-3k nodes and above).

In the specific would be nice to have a consul-agent that just offers the http/grpc API cache and the DNS interface and drop everything around:
- memberlist
- gossip protocol
- checks
- Network coordinates

Basically have an agent that acts just like a local DB that tools like service mesh/discovery can leverage to read from.
i'd love to start a discussion with the team here for understanding if something like a lightweight agent could be even implemented or just adding features gates flags to the existing agent is a possible alternative

Review the existing Consul agent and server responsibilities, focusing on the HTTP/gRPC API cache and DNS interface described in the issue. Compare the scalability implications of removing memberlist, gossip, checks, and network coordinates versus adding feature gates. Done would be a documented feasibility decision or an agreed implementation design.

Written by the indexing model from the issue text.