Migrate to the new chunk-oriented step model

Spring Batch 6.0 deprecates StepBuilder.chunk(int, PlatformTransactionManager) in favor of a new chunk-oriented model, where the transaction manager is configured through ChunkOrientedStepBuilder.transactionManager(PlatformTransactionManager). Replaces chunk(chunkSize, transactionManager) with chunk(chunkSize).transactionManager(transactionManager), but only where every other method in the builder chain has an equivalent on ChunkOrientedStepBuilder. The new model dropped the Spring Retry based chunk and retry APIs without a drop-in replacement, so chains calling backOffPolicy, retryPolicy, retryContextCache, keyGenerator, noRetry, noRollback, noSkip, processorNonTransactional, readerIsTransactionalQueue, chunkOperations, stepOperations, exceptionHandler, listener(RetryListener), chunk(CompletionPolicy, PlatformTransactionManager) or taskExecutor(TaskExecutor) with a non-async executor are left untouched, and remain a manual migration step. See the Spring Batch 6.0 migration guide.