[TENE-948] Run reindexing on production
Turned out, there were few flaws in previous solution, during long-running process for instance reindexing source with significant amount of records, OOM occured. Main cause was to use Transactional annotation for whole process, which internally kept references. Additionally simplified process with just async annotation without additional completableFuture, and finally field extraction from xml was rebuilt to use stax with proper resource handling. This MR resolved them all.