Tracing through KafkaChannel

[Harwayne]

Problem
A request made to the KafkaChannel should generate traces that link the request to the subscribers. It should either use an existing Trace if present, or create a new Trace if one isn't.

The trace from the Channel to any subscribers MUST be annotated with the subscription's name.

Persona:
System Integrator

Exit Criteria
Each of the following generate a trace that includes both the incoming request and the request to any subscribers. The trace from the Channel to any subscribers MUST be annotated with the subscription's name:

• A request sent to an KafkaChannel without any trace information.
• A request sent to an KafkaChannel with trace information in the HTTP headers (B3 format).
• A request sent to an KafkaChannel with trace information in the Cloud Event's traceparent attribute, but not in the HTTP headers.

Note that this is very similar to knative/eventing#1757

[slinkydeveloper]

I duplicated the issue here 😄 : #1139

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[slinkydeveloper]

This is solved