[KIP-932] use int64 for offset count in share ack commit offsets list

[Kartik (sage-mode-hunter)]

Offset count overflow in rd_kafka_share_build_partition_offsets_list:

• total_offsets is a 32-bit int but sums int64 ranges from broker AcquiredRecords; past INT_MAX it overflows
• the overflowed value sizes rd_kafka_share_partition_offsets_new while the fill loop writes one int64 per offset over the full range
• offset_idx is also int and can wrap to a negative index
• the sibling rd_kafka_share_build_response_rko already keeps this count in int64_t

Widened both to int64_t to match the int64 offsets array and that sibling.

[confluent-cla-assistant]

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[Kartik (sage-mode-hunter)]

i have signed the CLA.

[Kartik (sage-mode-hunter)]

Pushed an empty commit to re-run the CLA check. Signed it on my end already, so hopefully this clears the status.

[Kartik (sage-mode-hunter)]

any update?