fix the issue that decimal divide not round. (#6471)

[ti-chi-bot]

This is an automated cherry-pick of #6471

What problem does this PR solve?

Issue Number: close #6393, close #6462, close #4488

Problem Summary: The result of decimal divide won't round at some precision.

What is changed and how it works?

add round logic

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

fix the issue that decimal divides not round in some precision.

[ti-chi-bot]

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[LittleFall]

major level bug need not to triage