statistics: fix wrong behavior for primary key' non-lite init stats (#53298)

[ti-chi-bot]

This is an automated cherry-pick of #53298

What problem does this PR solve?

Issue Number: ref #37548

Problem Summary:

What changed and how does it work?

primary key's is_index is false. so it cannot load the topn. it's stats cannon be set as AllFull.

Check List

Tests

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

according to #37548, it's result is right.

• 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

[hawkingrei]

Don't fix it. Because this bug is not in v6.1

[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	00571e5	link	true	/test unit-test
idc-jenkins-ci-tidb/mysql-test	00571e5	link	true	/test mysql-test
idc-jenkins-ci-tidb/check_dev	00571e5	link	true	/test check-dev

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[ti-chi-bot]

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