This mimics xDS's discovery protocol where you must request a resource
explicitly for the exporting side to send those events to you.
As part of this I aligned the overall ResourceURL with the TypeURL that
gets embedded into the encoded protobuf Any construct. The
CheckServiceNodes is now wrapped in a better named "ExportedService"
struct now.
Peer replication is intended to be between separate Consul installs and
effectively should be considered "external". This PR moves the peer
stream replication bidirectional RPC endpoint to the external gRPC
server and ensures that things continue to function.
Matt Keeler