KIP-635 — GetOffsetShell: support for multiple topics and consumer configuration override

Accepted Kafka 3.0 Admin

Extends `GetOffsetShell` (via `kafka-get-offsets.sh`) to support querying multiple topics in a single invocation, adds `--bootstrap-servers` as an alias for `--broker-list`, and allows passing additional consumer configuration overrides. The tool currently accepts only a single topic per invocation and uses the non-standard `--broker-list` argument name, requiring users to script around it to fetch offsets for multiple topics.

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