ddl: rename const to common, separate its test [1/6]

[xhebox]

What problem does this PR solve?

Problem Summary: Separate from #22415, 1/6 patch from the large PR.

Check List

Tests

• Unit test
• Integration test

Release note

• No release note

[wjhuang2016]

/lgtm

[morgo]

/LGTM

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• morgo
• wjhuang2016

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[xhebox]

/merge

[ti-chi-bot]

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

Details

Commit hash: 35dea6c

[ti-chi-bot]

@xhebox: Your PR was out of date, I have automatically updated it for you.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

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