fixes #29: Faster record producing - removes blocks on Future and processes results asynchronously

[astubbs]

Performance improvement for sending records.

Checklist

• [ ] Documentation (if applicable)
• [ ] Changelog
• [ ] consider blocking work retrieval during PM commit lock - move the write lock from tx start to work offset retrieval (controller cannot get offsets until all in flight records are finished processing and sent records ack'd)
• [ ] Auto increase commit frequency to same as KS - log at info
• [ ] Clarify that XXX will have more reduction in potential duplicate processing after failure for records that taken during tx committing

Blocked by:

• #355