dm: fix lag keeps growing when failed ddl is skipped and no following ddl (#9607)

[ti-chi-bot]

This is an automated cherry-pick of #9607

What problem does this PR solve?

Issue Number: close #9605

What is changed and how it works?

• reset recorded ts on syncer restart

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• test using steps in the issue, before the change, lag keeps growing, became 0 after this pr

before 

➜  dm curl -s "127.0.0.1:8361/metrics" | grep -v '#'| grep dm_syncer_replication_lag_gauge
dm_syncer_replication_lag_gauge{source_id="mysql-3307",task="test",worker="worker-1"} 303
➜  dm curl -s "127.0.0.1:8361/metrics" | grep -v '#'| grep dm_syncer_replication_lag_gauge
dm_syncer_replication_lag_gauge{source_id="mysql-3307",task="test",worker="worker-1"} 313


after
➜  dm curl -s "127.0.0.1:8361/metrics" | grep -v '#'| grep dm_syncer_replication_lag_gauge
dm_syncer_replication_lag_gauge{source_id="mysql-3307",task="test",worker="worker-1"} 0
➜  dm curl -s "127.0.0.1:8361/metrics" | grep -v '#'| grep dm_syncer_replication_lag_gauge
dm_syncer_replication_lag_gauge{source_id="mysql-3307",task="test",worker="worker-1"} 0

• No code

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

fix lag keeps growing when failed ddl is skipped and no following ddl

[ti-chi-bot]

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[ti-chi-bot]

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This pull-request has been approved by: okJiang

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