Console output and log message not accurate when import data with dup records using lightning tidb backend.

[fubinzh]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Lightning import some data with few duplicate rows using tidb end, conflict.strategy = 'replace';

# cat /tmp/tidb-lightning.toml
[lightning]                                       
level = 'debug'                                   
[mydumper]                                        
filter = ['coms.PK_*']                            
[conflict]                                        
strategy = 'replace'     

2, Lighting import finishes

2. What did you expect to see? (Required)

Lightning import should succeed as there are only 5 duplicate rows.
And the info in lightning console output and log should be accurate.

3. What did you see instead (Required)

Lightning logs says that "Detect 5 conflict errors in total, please refer to table lightning_task_info.conflict_view for more details"
However, the conflict rows will not be recorded for strategy = "replace" in TiDB backend per https://docs.pingcap.com/zh/tidb/stable/tidb-lightning-configuration, also validated that there is no records in the tables actually.

[2024/06/17 15:04:36.751 +00:00] [INFO] [import.go:578] ["the whole procedure completed"] [takeTime=1h6m44.025684115s] []
[2024/06/17 15:04:36.751 +00:00] [WARN] [errormanager.go:1089] ["Detect 5 conflict errors in total, please refer to table `lightning_task_info`.`conflict_view` for more details"]
[2024/06/17 15:04:36.751 +00:00] [INFO] [main.go:110] ["tidb lightning exit"] [finished=true]

4. What is your TiDB version? (Required)

Release Version: v8.2.0-alpha
Git Commit Hash: 26d1096
Git Branch: heads/refs/tags/v8.2.0-alpha
Go Version: go1.21.10
UTC Build Time: 2024-06-17 11:41:27
Race Enabled: false

[fubinzh]

/component lightning

[fubinzh]

/severity minor