Optimize communication between Conduit and standalone connectors

[hariso]

Feature description

Currently, Conduit and standalone connectors communicate via gRPC over TCP. One option that's likely going to be faster is using gRPC over a Unix domain socket. This takes advantage of the fact that Conduit and the standalone connectors are running on the same host.

Useful resources:

• https://github.com/grpc/grpc/blob/master/doc/naming.md
• https://www.mpi-hd.mpg.de/personalhomes/fwerner/research/2021/09/grpc-for-ipc/