sqlmodel(dm): generate key in lower case (#9498)

[ti-chi-bot]

This is an automated cherry-pick of #9498

What problem does this PR solve?

Issue Number: close #9489

What is changed and how it works?

convert the key to lower case could detect case insensitive conflict, it may introduce fake conflict when the collation is case sensitive, but it won't affect the correctness of dm, because it only introduces a sync point

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

generate load with conflicting key of the schema mentioned in the issue, before the change the replication could be broken within tens of minutes, after the change, it has been running for over 10 hours without issue

• No code

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lance6716

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[lance6716]

/retest