Fix clang-tidy warnings for a batch of files

[dragonly]

What problem does this PR solve?

Issue Number: close #2886, close #2887, close #2889, close #2890, close #2891

Problem Summary:

What is changed and how it works?

Proposal: xxx

What's Changed:

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch:

Check List

Tests

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

Side effects

Release note

None

[ti-chi-bot]

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• fuzhe1989

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[fuzhe1989]

nit: declare it as private (also the ctor) and rename it as getInternal.

[dragonly]

/run-all-tests

[fuzhe1989]

/merge

[ti-chi-bot]

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: ba6c8c4

[ti-chi-bot]

@dragonly: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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