ddl: Only warn of subpartitions, still allow first level partitioning (#41207) | tidb-test=pr/2193

[ti-chi-bot]

This is an automated cherry-pick of #41207

What problem does this PR solve?

Issue Number: close #41198 , close #41200

Problem Summary:
For LIST partitioning, it did not check if SUBPARTITION was used and just stripped the subpartition part
For RANGE and HASH partitioning it stripped all partitioning and added a warning that such partitioning was not supported.

What is changed and how it works?

Combine the two behaviours:
Strip the subpartitioning from the CREATE TABLE statement and issue a warning.

Check List

Tests

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

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.

If CREATE TABLE includes subpartitions, keep the normal partitioning and skip the subpartitioning + add a warning.

[ti-chi-bot]

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[mjonss]

/retest

[mjonss]

/retest

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@73892ba). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

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[mjonss]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mjonss, tiancaiamao

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Needs approval from an approver in each of these files:

• OWNERS [mjonss,tiancaiamao]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-02 09:33:26.735576893 +0000 UTC m=+264290.677925424: ☑️ agreed by tiancaiamao.
• 2023-08-02 10:12:17.860040937 +0000 UTC m=+266621.802389468: ☑️ agreed by mjonss.

[mjonss]

/retest