Add Logging to the Telemetry Service

[nraultwang]

Add a gRPC log handler to the Telemetry service to enable remote processes to send logs to the headnode's Loki database.

The code changes to add this log handler are minimal:

1. Install the panoseti-grpc package and
2. Call make_grpc_logger with attach_to_root=true while creating a global logger to attach the gRPC log handler.

After attaching this log handler to the control code, we can view the commands observers have run on a Grafana dashboard panel, connected to Loki: