Handshake is a common handshake that is shared by plugin and host.

PluginMap is the map of plugins we can dispense.

GRPCClient is an implementation of KV that talks over RPC.

Here is the gRPC server that GRPCClient talks to.

This is the implementation of plugin.Plugin so we can serve/consume this.

KV is the interface that we're exposing as a plugin.