Kafka Share Group support

[Shekharrajak]

Doris supports traditional Kafka's assign() API where Parallelism is capped by partition count and Partition skew is unaddressable.

Kafka 4.0 introduced Share Groups (KIP-932): a consumption model where multiple consumers in a group share access to the same partitions without exclusive ownership.

The key features it brings to Doris:

• Decoupled Parallelism: Consumption concurrency is no longer limited by the number of Kafka partitions, allowing for more elastic scaling.
• Automatic Load Balancing: Records are distributed to available consumers on a first-come, first-served basis, effectively eliminating partition skew.
• Record-Level Reliability: Individual records are tracked via an ACQUIRED/ACCEPTED/RELEASED state, ensuring precise delivery even if a task fails.

Ref #63190