WIP: ddl_puller.go: fix DDLs are ignored when schema versions are out of order

[wlwilliamx]

What problem does this PR solve?

Issue Number: close #11714

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• 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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.1487%. Comparing base (1da37a2) to head (880e28f).
Report is 1 commits behind head on master.

Additional details and impacted files

Components	Coverage Δ
cdc	59.6424% <100.0000%> (+0.0095%)	⬆️
dm	50.0288% <ø> (-0.0154%)	⬇️
engine	53.2110% <ø> (-0.0170%)	⬇️

Flag	Coverage Δ
unit	55.1487% <100.0000%> (-0.0036%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

@@               Coverage Diff                @@
##             master     #11733        +/-   ##
================================================
- Coverage   55.1522%   55.1487%   -0.0036%     
================================================
  Files          1001       1001                
  Lines        136524     136520         -4     
================================================
- Hits          75296      75289         -7     
- Misses        55718      55720         +2     
- Partials       5510       5511         +1     

[wlwilliamx]

/retest