pkg/causality(cdc): refactor and simplify conflict detector (#10954)

[ti-chi-bot]

This is an automated cherry-pick of #10954

What problem does this PR solve?

Issue Number: close #10973

What is changed and how it works?

• Remove some useless and redundant logic.
• Move sortAndDedupHashes to pkg/causality/internal/slots.go, since it is used to solve the false positive problem caused by hash conflicts in slots.
• For txnEvent interface, rename GenSortedDedupKeysHash to ConflictKeys to ensure semantic consistency, because the implementers should not care about internal implementations of conflict_detector.

Check List

Tests

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

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