Un-deprecate local offset storage

[lpsinger]

Description

This is a feature request to un-deprecate and continue supporting local offset storage. We are operating a Kafka cluster that is open to users who are not fully trusted; we do not want to have to allocate ACLs for consumer groups for our users and we do not want to store our consumers' offsets on our brokers.

How to reproduce

All of the offset.store.* properties are shown as deprecated in https://github.com/confluentinc/librdkafka/blob/master/CONFIGURATION.md.

Checklist

IMPORTANT: We will close issues where the checklist has not been completed.

Please provide the following information:

• [x] librdkafka version (release number or git tag): v2.0.2
• [ ] Apache Kafka version: v2.0.2
• [ ] librdkafka client configuration: N/A
• [ ] Operating system: N/A
• [ ] Provide logs (with debug=.. as necessary) from librdkafka N/A
• [ ] Provide broker log excerpts N/A
• [ ] Critical issue N/A

[emasab]

Thanks @lpsinger we're evaluating this use case and will see what can be done