local sort，the preformance may drop because of coprocessor timeout when import into 10T data

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
import 10 T data with local sort.
it spend 5h12m and retry 3 time to finish checksum

coprocessor keeping timeout when import into large data lead to too much compaction。
We should do some optimization on this

### 2. What did you expect to see? (Required)
the performance should not drop too much

### 3. What did you see instead (Required)
the performance drop a lot
### 4. What is your TiDB version? (Required)

master