schema(ticdc): add unit test for handle key column

[asddongmen]

What problem does this PR solve?

Issue Number: close #8548

What is changed and how it works?

Check List

Tests

• Unit test

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hicqu
• overvenus

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[asddongmen]

/merge

[ti-chi-bot]

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

Commit hash: 0c07833

[ti-chi-bot]

@asddongmen: Your PR was out of date, I have automatically updated it for you.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

trigger some heavy tests which will not run always when PR updated.

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.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[asddongmen]

/run-verify