feat: add IPTraceID into flow struct

This change introduces the IPTraceID field to the Hubble protobuf. This allows
IP-based tracing information to be propagated and associated with flows
observed by Hubble.

The following changes are included:
- A new `IPTraceID` message type is defined in `flow.proto`, containing
the trace ID and the IP option type.
- The Hubble parser is updated to decode the IP trace ID from monitor
events (both drop and trace notifications) and populate the `ip_trace_id`
field in the resulting `Flow` message.
- The Hubble printer is updated to display the IP trace ID in the
output.

Signed-off-by: Ben Bigdelle <bigdelle@google.com>

Author: Bigdelle

api/v1/flow/README.md

@@ -24,6 +24,7 @@
     - [ICMPv6](#flow-ICMPv6)
     - [IP](#flow-IP)
     - [IPCacheNotification](#flow-IPCacheNotification)
+    - [IPTraceID](#flow-IPTraceID)
     - [Kafka](#flow-Kafka)
     - [Layer4](#flow-Layer4)
     - [Layer7](#flow-Layer7)
@@ -312,6 +313,7 @@ EventTypeFilter is a filter describing a particular event type.
 | trace_observation_point | [TraceObservationPoint](#flow-TraceObservationPoint) |  | Only applicable to cilium trace notifications, blank for other types. |
 | trace_reason | [TraceReason](#flow-TraceReason) |  | Cilium datapath trace reason info. |
 | file | [FileInfo](#flow-FileInfo) |  | Cilium datapath filename and line number. Currently only applicable when Verdict = DROPPED. |
+| ip_trace_id | [IPTraceID](#flow-IPTraceID) |  | IPTraceID relates to the trace ID in the IP options of a packet. |
 | drop_reason_desc | [DropReason](#flow-DropReason) |  | only applicable to Verdict = DROPPED. |
 | is_reply | [google.protobuf.BoolValue](#google-protobuf-BoolValue) |  | is_reply indicates that this was a packet (L4) or message (L7) in the reply direction. May be absent (in which case it is unknown whether it is a reply or not). |
 | debug_capture_point | [DebugCapturePoint](#flow-DebugCapturePoint) |  | Only applicable to cilium debug capture events, blank for other types |
@@ -381,6 +383,7 @@ multiple fields are set, then all fields must match for the filter to match.
 | node_labels | [string](#string) | repeated | node_labels filters on a list of node label selectors. Selectors support the full Kubernetes label selector syntax. |
 | ip_version | [IPVersion](#flow-IPVersion) | repeated | filter based on IP version (ipv4 or ipv6) |
 | trace_id | [string](#string) | repeated | trace_id filters flows by trace ID |
+| ip_trace_id | [uint64](#uint64) | repeated | ip_trace_id filters flows by IPTraceID |
 | experimental | [FlowFilter.Experimental](#flow-FlowFilter-Experimental) |  | experimental contains filters that are not stable yet. Support for experimental features is always optional and subject to change. |
 
 
@@ -512,6 +515,22 @@ L7 information for HTTP flows. It corresponds to Cilium's [accesslog.LogReco
 
 
 
+<a name="flow-IPTraceID"></a>
+
+### IPTraceID
+
+
+
+| Field | Type | Label | Description |
+| ----- | ---- | ----- | ----------- |
+| trace_id | [uint64](#uint64) |  |  |
+| ip_option_type | [uint32](#uint32) |  |  |
+
+
+
+
+
+
 <a name="flow-Kafka"></a>
 
 ### Kafka