Fix decimal floor/ceil (#10365) (#10364)

[ti-chi-bot]

This is an automated cherry-pick of #10364

What problem does this PR solve?

Issue Number: close #10365, close #3496, ref pingcap/tidb#63086

Problem Summary:

What is changed and how it works?

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

None

[ChangRui-Ryan]

/test pull-integration-test

[windtalker]

lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker, wshwsh12

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• OWNERS [windtalker,wshwsh12]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-09-09 01:26:41.183467059 +0000 UTC m=+324667.743348555: ☑️ agreed by windtalker.
• 2025-09-09 01:59:56.559183471 +0000 UTC m=+326663.119064967: ☑️ agreed by wshwsh12.

[ChangRui-Ryan]

/retest