hot scheduler is not fast enough for insert workload

## Enhancement Task
![Image](https://github.com/user-attachments/assets/5a814bf7-9b07-4ef1-87f9-575f6525c6ad)
sometimes hot scheduler is not fast enough for insert workload with shard bit.

workload is https://github.com/pingcap/ticdc/pull/672/files#diff-f9b50c2d97eed7c3b6899dc697ec76a370958cebe183141eef95b5119c23d5bfR26-R54