Fix incompatible behavior with TiDB when casting float into string

[solotzg]

What problem does this PR solve?

Issue Number: close #9697
Problem Summary:

• same problem in unexpected result: casting real to string  tikv/tikv#16974, query with distinct gets a unexpected result tidb#51109
• tidb tools (such as lightning) rely on crc function of tidb. crc module needs to cast basic type into string at first, which means all behavior about casting into str cannot be modified in order to keep backward compatibility.

What is changed and how it works?

Fix incompatible behavior with TiDB when casting floating into string
- always convert the format into non-exponential representation

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

[solotzg]

/run-all-tests

[windtalker]

lgtm

[yibin87]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker, yibin87

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• OWNERS [windtalker,yibin87]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-05 05:31:54.620262994 +0000 UTC m=+1305702.239917509: ☑️ agreed by windtalker.
• 2024-12-05 07:42:14.991714577 +0000 UTC m=+1313522.611369093: ☑️ agreed by yibin87.