Packet Forwarding Engine DDoS sensor support with JTI

JTI supports distributed denial-of-service (DDoS) telemetry sensors. To stream DDoS statistics from a device to a collector, include the resource path /junos/system/linecard/ddos/) in a subscription. You can stream statistics using UDP (native) or Juniper proprietary gRPC and gNMI. This feature supports the Openconfig data model junos/ui/openconfig/yang/junos-ddos.yang. Currently, there are 45 packet types for DDoS. To maintain a reasonably sized data stream, data is exported for all protocols that have traffic using the zero-suppression model.