Update gRPC/etcd packages

[Tony Allen]

Update gRPC/etcd packages

It appears there are deprecated gRPC packages ("google.golang.org/grpc/naming") being used, which make upgrading to more recent versions (grpc@v1.39.0) difficult. Using the replacements for the deprecated libraries would also require upgrading etcd to version 3.5+, since the version of etcd being used has a reliance on the older gRPC version as well.

Is there a reason we've pinned the gRPC/etcd versions to what they currently are? If not, would there be any objection to a PR modernizing them?