[KIP-932] : Add tests for share consumer - 1/N

[Kaushik Raina (k-raina)]

Summary

• Basic consuming and message - reading records correctly: values,
  keys, headers, header order, timestamps, empty/null payloads, multi-partition, batch-size caps,
  oversized records, compression, and rejecting cross-thread use
• Subscription handling - subscribing/unsubscribing behavior: multiple topics,
  repeated/incremental subscribes, empty-list and bad topic names, subscribing before a topic exists,
  and re-subscribing to the same topic

[confluent-cla-assistant]

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[sonarqube-confluent]

Quality Gate failed

Failed conditions
1.1% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube