feat(consumer): return err from offsets commit

[dnwe]

This changes the ConsumerGroupSession and OffsetManager interface in a way that’s compatible for users of these interfaces, but incompatible for implementers.

Contributes-to: IBM/sarama#2417

[dnwe]

As noted that even our own internals fail due the errcheck linter on offsetManager.Commit, it probably makes sense to defer this to v2

[github-actions[bot]]

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