[kafka] do not use message creation context as a parent for consumer spans

[lachmatt]

Why

Fixes #3434

• CHANGELOG.md is updated.
• Documentation is updated.
• New features are covered by tests.

[RassK]

@lachmatt do you have any images how does it look like?

I'm a bit confused about this description. To me it seems there should be 2 spans? receive (that includes polling time) that is linked to consume span? or receive = consume?
open-telemetry/opentelemetry-demo#1538 (comment)

[lachmatt]

@lachmatt do you have any images how does it look like?

I'm a bit confused about this description. To me it seems there should be 2 spans? receive (that includes polling time) that is linked to consume span? or receive = consume? open-telemetry/opentelemetry-demo#1538 (comment)

Receive is type of consumer span/operation. Consume is the name of the method being instrumented.
There will be single span on consumer side, with link to the propagated context.

[RassK]

@lachmatt ah right, so the linked propagated context is actually kafka publish?