[receiver/kafkareceiver] Add 'topic' attribute to kafka internal metrics

[petern48]

Description

Add 'topic' attribute to kafka existing internal metrics.

Link to tracking issue

Fixes #35336

Testing

Updated the existing kafkareceiver_test.go

Documentation

Changelog

[petern48]

Not sure why the changelog action is failing. Seems correct to me and running that bash command locally gives me the right output.

> git diff --diff-filter=A --name-only $(git merge-base origin/main kafka_topic_metric_attr) kafka_topic_metric_attr ./.chloggen | grep -c \\.yaml
1

[MovieStoreGuy]

@axw , would the exporter also benefit from adding internal metrics like this?

[axw]

LGTM, thanks @petern48!

@MovieStoreGuy yes, I would say so. I know I bang on about franz-go a bit, but if at some point we switch over to it, we can potentially make use of its kotel instrumentation: https://github.com/twmb/franz-go/tree/master/plugin/kotel#metrics. It should be easier to keep the metrics consistent then.