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.
* Install `buf` instead of `protoc`
* Created `buf.yaml` and `buf.gen.yaml` files in the two proto directories to control how `buf` generates/lints proto code.
* Invoke `buf` instead of `protoc`
* Added a `proto-format` make target.
* Committed the reformatted proto files.
* Added a `proto-lint` make target.
* Integrated proto linting with CI
* Fixed tons of proto linter warnings.
* Got rid of deprecated builtin protoc-gen-go grpc plugin usage. Moved to direct usage of protoc-gen-go-grpc.
* Unified all proto directories / go packages around using pb prefixes but ensuring all proto packages do not have the prefix.
