feat(writer): the RollingFileWriter closes files in background when concurrency is set#1571

fvaleye wants to merge 2 commits intoapache:mainapache/iceberg-rust:mainfrom

fvaleye:feat/improve-rolling-writer-closing-in-backgroundfvaleye/iceberg-rust:feat/improve-rolling-writer-closing-in-backgroundCopy head branch name to clipboard