message: [grafana] Update network dashboard to use new histogram metrics
  Now uses `irate(libra_network_direct_send_bytes_sum)` to get total
  outbound throughput for DirectSend Protocol.
  Closes:
  Approved by: bothra90
diff: "steppedLine": false,
  "targets": [
  {
  - "expr": "irate(libra_network_direct_send_bytes{state=\"sent\"}[1m])",
  + "expr": "irate(libra_network_direct_send_bytes_sum{state=\"sent\"}[1m])",
  "format": "time_series",
  "intervalFactor": 1,
  "legendFormat": "{{peer_id}}",
  "steppedLine": false,
  "targets": [
  {
  - "expr": "irate(libra_network_direct_send_bytes{state=\"received\"}[1m])",
  + "expr": "irate(libra_network_direct_send_bytes_sum{state=\"received\"}[1m])",
  "format": "time_series",
  "intervalFactor": 1,
  "legendFormat": "{{peer_id}}",
  