Add network metrics to RPC

[gavv]

We need a way to obtain network metrics of a virtual device via RPC.

RPC allows to fetch device info (RvDeviceInfo), which includes sender and receiver config:

    // Network configuration of device.
    // Parameters of network sender or receiver.
    oneof NetworkConfig
    {
        // Configuration for sender device.
        // Should be used if device type is RV_DEVICE_TYPE_SENDER.
        RvSenderConfig sender_config = 7;

        // Configuration for receiver device.
        // Should be used if device type is RV_DEVICE_TYPE_RECEIVER.
        RvReceiverConfig receiver_config = 8;
    }

Similarly, we can add NetworkMetrics field, and fill it with sender/receiver metrics (depending on devices type), that are available from the streaming library. (Roc Toolkit 0.4 exports only e2e_latency and connection_count metrics; 0.5 will export more metrics).

Related files:

• rpc/driver_protocol.proto - defines RPC interface and RvDeviceInfo
• driver/device_defs.hpp - defines C++ structs including DeviceInfo
• driver/rpc_serdes.cpp - defines mapping between C++ structs and protobuf RPC messages
• driver/device.hpp - defines object created for every device, it returns device info, and holds a reference to Transceiver (a base class for Sender and Receiver)
• driver/sender.hpp - created for sender devices; holds a pointer to roc_sender, from where we can obtain sender metrics (via roc_sender_query())
• driver/receiver.hpp - created for receiver devices; holds a pointer to roc_receiver, from where we can obtain receiver metrics (via roc_receiver_query())
• tool/print.cpp - code that prints device info to console on the client side, we'll need to print metrics here

After updating these files, metrics should appear in the output of roc-vad device list --detail and roc-vad device show commands.

See also:

• README and HACKING.md
• Roc Toolkit API