Detect data inconsistency after switching table mode

[hongyunyan]

Bug Report

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1. Minimal reproduce step (Required)

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

3. What did you see instead (Required)

case 情况与日志
https://github.com/pingcap/endless/blob/d8015156435e768921a3c1a2e48bcc2b59267dba/testcase/tiflash/consistency/consistency_test.go#L98

[2022/07/28 19:22:15.051 +08:00] [INFO] [consistency_test.go:515] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=fast]
[2022/07/28 19:22:15.206 +08:00] [INFO] [consistency_test.go:504] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=normal]
[2022/07/28 19:22:15.832 +08:00] [INFO] [verify.go:127] ["verify successfully"] [tikv="[100000000]"] [tiflash="[100000000]"]
[2022/07/28 19:22:25.833 +08:00] [INFO] [consistency_test.go:515] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=fast]
[2022/07/28 19:22:25.992 +08:00] [INFO] [consistency_test.go:504] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=normal]
[2022/07/28 19:22:26.633 +08:00] [INFO] [verify.go:127] ["verify successfully"] [tikv="[100000000]"] [tiflash="[100000000]"]
[2022/07/28 19:22:36.635 +08:00] [INFO] [consistency_test.go:515] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=fast]
[2022/07/28 19:22:36.788 +08:00] [INFO] [consistency_test.go:504] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=normal]
[2022/07/28 19:22:37.475 +08:00] [INFO] [verify.go:127] ["verify successfully"] [tikv="[100000000]"] [tiflash="[100000000]"]
[2022/07/28 19:22:47.475 +08:00] [INFO] [consistency_test.go:515] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=fast]
[2022/07/28 19:22:47.629 +08:00] [INFO] [consistency_test.go:504] ["convert tiflash mode"] ["db name"=test] ["table names"="[t]"] [mode=normal]
[2022/07/28 19:22:48.229 +08:00] [ERROR] [consistency_test.go:508] ["check consistence error"] ["db name"=test] [sql="select count(*) from t"] [error="result inconsistent tso 434898827405164654, tikv: [100000000], tiflash [100000750]"]

4. What is your TiFlash version? (Required)

v6.2

[lidezhu]

Seems the problem is caused by #5397