Various fixes & improvements
- feat: Split the Message interface to better support batching steps (134) by lynnagara
- feat: Remove BatchProcessingStrategyFactory from Arroyo (138) by lynnagara
- docs: Add docstring for MessageRejected (146) by lynnagara
- feat: Increase log level during consumer shutdown (144) by lynnagara
- feat: Remove ProduceAndCommit (145) by lynnagara