0.21.1-fix3

What's Changed

• fix: use global pool but not dedicated pool for every index by @chyezh in #1
• fix: use different thread pool for scheduler and merger by @chyezh in #2
• enhance: make all index operation async scheduled by tokio by @chyezh in #3

New Contributors

• @chyezh made their first contribution in #1

Full Changelog: https://github.com/milvus-io/tantivy/commits/0.21.1-fix3