* Protobuf Modernization
Remove direct usage of golang/protobuf in favor of google.golang.org/protobuf
Marshallers (protobuf and json) needed some changes to account for different APIs.
Moved to using the google.golang.org/protobuf/types/known/* for the well known types including replacing some custom Struct manipulation with whats available in the structpb well known type package.
This also updates our devtools script to install protoc-gen-go from the right location so that files it generates conform to the correct interfaces.
* Fix go-mod-tidy make target to work on all modules
Previously, public referred to gRPC services that are both exposed on
the dedicated gRPC port and have their definitions in the proto-public
directory (so were considered usable by 3rd parties). Whereas private
referred to services on the multiplexed server port that are only usable
by agents and other servers.
Now, we're splitting these definitions, such that external/internal
refers to the port and public/private refers to whether they can be used
by 3rd parties.
This is necessary because the peering replication API needs to be
exposed on the dedicated port, but is not (yet) suitable for use by 3rd
parties.
Matt Keeler