[Backport 7.75.x] Fix Protobuf with schema registry usage for kafka-actions

[datadog-agent-integrations-bot]

Backport 19bc7d4 from #22265.

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What does this PR do?

Kafka actions were migrated to kafka-actions (from kafka_consumer).
However, I merged this fix to kafka_consumer, that I didn't migrate to kafka-actions.

On top of that, there is an edge case (when there is a single message in a protobuf) that I fixed + added a unit test in both kafka_consumer & kafka_actions.

I will remove that logic from kafka_consumer in the near future and only rely on kafka-actions.

Motivation

Moving to kafka-actions for all actions performed on kafka.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

❌ Patch coverage is 82.85714% with 12 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (7.75.x@72909fe). Learn more about missing BASE report.

Additional details and impacted files

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[datadog-datadog-prod-us1]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

❄️ 1 New flaky test detected

test_check_kafka from test_integration.py (Datadog) (Fix with Cursor)

KafkaError{code=_TRANSPORT,val=-195,str="Failed to get metadata: Local: Broker transport failure"}

ℹ️ Info

🧪 All tests passed

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