Add support for local chunking #5021
Description
In many cases, local chunking is sufficient, and the added complexity of remote chunking is not justified. The JVM is getting better and better in terms of concurrency constructs, and it would be great to add support for local chunking in Spring Batch and leverage the power of a single JVM.
The idea is to introduce an item writer similar to ChunkMessageChannelItemWriter, but instead of sending chunk requests over the wire to remote workers, it would submit them to local worker threads from a task executor. Each thread would then process a chunk separately in its own transaction.
This is an additional concurrency technique at chunk level compared to the item level concurrency introduced in #4955