ddl: still use write count for ingest worker

[YangKeao]

What problem does this PR solve?

Issue Number: close #64602

Problem Summary:

What changed and how does it work?

1. Revert the counting part for index ingest worker. Let it still use the count of indexes.
2. Remove the totalCount in tableScanWorker, because it's not used.
3. Add ReadRowCnt in SubtaskSummary.
4. Add a test for scanRecords to show that the count depends on how cops are handled.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[YangKeao]

/hold The row count is not as expected

[codecov]

Codecov Report

❌ Patch coverage is 78.12500% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.9567%. Comparing base (3082092) to head (df9ec19).
⚠️ Report is 858 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #64655        +/-   ##
================================================
+ Coverage   74.7209%   74.9567%   +0.2358%     
================================================
  Files          1888       1889         +1     
  Lines        515161     515831       +670     
================================================
+ Hits         384933     386650      +1717     
+ Misses       106411     105430       -981     
+ Partials      23817      23751        -66     

Flag	Coverage Δ
integration	48.3632% <0.0000%> (+0.2042%)	⬆️
unit	72.5564% <80.6451%> (+0.2747%)	⬆️

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

Components	Coverage Δ
dumpling	52.8700% <ø> (ø)
parser	∅ <ø> (∅)
br	63.1843% <ø> (+0.0030%)	⬆️

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[YangKeao]

/retest

[YangKeao]

/unhold

This one is fine now 😆

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: wjhuang2016
Once this PR has been reviewed and has the lgtm label, please assign d3hunter for approval. For more information see the Code Review Process.
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Details

Needs approval from an approver in each of these files:

• OWNERS [wjhuang2016]
• pkg/ddl/OWNERS [wjhuang2016]
• pkg/disttask/OWNERS [wjhuang2016]
• pkg/executor/importer/OWNERS
• pkg/lightning/OWNERS

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-11-27 12:48:30.001160102 +0000 UTC m=+793473.650354559: ☑️ agreed by wjhuang2016.