The field Wait_ts is not updated in slow log for the sqls which are in the same transaction

[TonsnakeLin]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set tidb_slow_log_threshold = 0
begin;
select * from t1 where id1 = 1;
select * from t1 where id2>3;

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

The two sqls above have different Wait_TS in slow log.

3. What did you see instead (Required)

The two sqls above have the same Wait_TS in slow log.

4. What is your TiDB version? (Required)

Release Version: v6.5.0-alpha-272-g35819ee
Edition: Community
Git Commit Hash: 35819ee
Git Branch: master
UTC Build Time: 2022-12-07 07:52:28
GoVersion: go1.19
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv