[WIP] automatically add summary for files without a summary

[CharLotteiu]

First-time contributors' checklist

• [ ] I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

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Which TiDB version(s) do your changes apply to? (Required)

• [ ] master (the latest development version)
• [ ] v5.0 (TiDB 5.0 versions)
• [ ] v4.0 (TiDB 4.0 versions)
• [ ] v3.1 (TiDB 3.1 versions)
• [ ] v3.0 (TiDB 3.0 versions)
• [ ] v2.1 (TiDB 2.1 versions)

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• [ ] Delete files
• [ ] Change aliases
• [ ] Need modification after applied to another branch
• [ ] Might cause conflicts after applied to another branch

[ti-chi-bot]

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[ti-chi-bot[bot]]

@CharLotteiu: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-verify	763cd6f558c70f7fd83201c4e58dea5b4c60b6c6	link	true	/test pull-verify

Full PR test history. Your PR dashboard.

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