Add proc net dev metrics to net stats

[bw-solana]

Problem

Need more detailed network metrics to understand ingress and egress bandwidth. Especially for seeing if NIC line rate is being saturated

Summary of Changes

Add collection/parsing/reporting of /proc/net/dev

[bw-solana]

Here's a snippet of the new metrics in action:

[2022-07-13T20:16:16.489522366Z INFO  solana_metrics::metrics] datapoint: net-stats-validator in_datagrams_delta=29262i no_ports_delta=0i in_errors_delta=0i out_datagrams_delta=26957i rcvbuf_errors_delta=0i sndbuf_errors_delta=0i in_csum_errors_delta=0i ignored_multi_delta=0i in_errors=45337200i rcvbuf_errors=45337200i sndbuf_errors=0i rx_bytes_delta=28973115i rx_packets_delta=29309i rx_errs_delta=0i rx_drops_delta=0i rx_fifo_delta=0i rx_frame_delta=0i rx_compressed_delta=0i rx_multicast_delta=0i tx_bytes_delta=29910513i tx_packets_delta=26963i tx_errs_delta=0i tx_drops_delta=0i tx_fifo_delta=0i tx_colls_delta=0i tx_carrier_delta=0i tx_compressed_delta=0i
[2022-07-13T20:16:18.492201831Z INFO  solana_metrics::metrics] datapoint: net-stats-validator in_datagrams_delta=50128i no_ports_delta=0i in_errors_delta=0i out_datagrams_delta=106674i rcvbuf_errors_delta=0i sndbuf_errors_delta=0i in_csum_errors_delta=0i ignored_multi_delta=0i in_errors=45337200i rcvbuf_errors=45337200i sndbuf_errors=0i rx_bytes_delta=39813055i rx_packets_delta=50167i rx_errs_delta=0i rx_drops_delta=0i rx_fifo_delta=0i rx_frame_delta=0i rx_compressed_delta=0i rx_multicast_delta=0i tx_bytes_delta=85306286i tx_packets_delta=106654i tx_errs_delta=0i tx_drops_delta=0i tx_fifo_delta=0i tx_colls_delta=0i tx_carrier_delta=0i tx_compressed_delta=0i
[2022-07-13T20:16:20.494072805Z INFO  solana_metrics::metrics] datapoint: net-stats-validator in_datagrams_delta=40076i no_ports_delta=0i in_errors_delta=0i out_datagrams_delta=24018i rcvbuf_errors_delta=0i sndbuf_errors_delta=0i in_csum_errors_delta=0i ignored_multi_delta=0i in_errors=45337200i rcvbuf_errors=45337200i sndbuf_errors=0i rx_bytes_delta=37364276i rx_packets_delta=40141i rx_errs_delta=0i rx_drops_delta=0i rx_fifo_delta=0i rx_frame_delta=0i rx_compressed_delta=0i rx_multicast_delta=0i tx_bytes_delta=26488448i tx_packets_delta=24059i tx_errs_delta=0i tx_drops_delta=0i tx_fifo_delta=0i tx_colls_delta=0i tx_carrier_delta=0i tx_compressed_delta=0i
[2022-07-13T20:16:22.498034180Z INFO  solana_metrics::metrics] datapoint: net-stats-validator in_datagrams_delta=37508i no_ports_delta=0i in_errors_delta=0i out_datagrams_delta=28591i rcvbuf_errors_delta=0i sndbuf_errors_delta=0i in_csum_errors_delta=0i ignored_multi_delta=0i in_errors=45337200i rcvbuf_errors=45337200i sndbuf_errors=0i rx_bytes_delta=36846657i rx_packets_delta=37543i rx_errs_delta=0i rx_drops_delta=0i rx_fifo_delta=0i rx_frame_delta=0i rx_compressed_delta=0i rx_multicast_delta=0i tx_bytes_delta=30924118i tx_packets_delta=28596i tx_errs_delta=0i tx_drops_delta=0i tx_fifo_delta=0i tx_colls_delta=0i tx_carrier_delta=0i tx_compressed_delta=0i

[jbiseda]

LGTM