GoLang based sharded client for DKV

[KalyanAkella]

We currently have a GoLang client impl. inside dkv/pkg/ctl/client.go, but this implementation needs to be extended in the following ways in order to make it compatible with the Java based impl.

Specifically, this issue is about enhancing the existing GoLang client in the following ways:

• extract the impl. into dkv/clients/go since that is where we intend to develop various DKV clients
• this new location will be another independent GOROOT with its own go.mod and go.sum files + Makefile.
• impl. support for clients-side sharding based on the Java client's impl.
• for hashing, use the XXHash impl. for GoLang here
• for caching/pooling GRPC connections, we can consider using ristretto
• integrate with StatsD and provide metrics for latencies and errors.
• build script changes to build GoLang client before building dkvctl, or perhaps we can choose to generate dkvctl directly from this GoLang client package itself