infoschema: fix sub_part in information_schema.statistics table (#55814)

[ti-chi-bot]

This is an automated cherry-pick of #55814

What problem does this PR solve?

Issue Number: close #55812

Problem Summary: We didn't set sub_part column correctly in information_schema.statistics table, just fix it.
Also found a bug related with mysql-tester. pingcap/mysql-tester#131

What changed and how does it work?

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

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None

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, lance6716

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-06 08:01:36.55394285 +0000 UTC m=+604221.071995774: ☑️ agreed by Defined2014.
• 2024-09-06 08:05:13.580794955 +0000 UTC m=+604438.098847880: ☑️ agreed by lance6716.