Add authentication to teos_cli

[sr-gi]

teos_cli is currently supposed to be used within the same machine as teosd, given the RPC server is offered in localhost and no authentication mechanism is offered. Exposing the RPC to the wild is highly unrecommended, since anyone would be able to interact with the tower.

An authentication method for the RPC server (gRPC) is needed in order to fix this.

[orbitalturtle]

Thinking of giving this a shot. Good ol' SSL?

[sr-gi]

gRPCoffers several authentication mechanisms AFAIK, but yeah I think SSL should do.

The goal is having something similar to bitcoind, where user and password is required. Currently we are using it through insecure channels (e.g. cli.grpc.insecure_channel(...)).