refactor/improve clarity: refactored and added more details about duplicate detection of tidb-lightning

[nova-xu]

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之前的冲突检测杂糅在backend导入模式的配置介绍中，并且比较简略，不是太清晰。我结合现有的内容，创建了一个新的页面解释冲突检测，加入了详细的例子以及更多关于冲突检测的细节。

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Thank you, and welcome to pingcap/docs-cn. 😃

[nova-xu]

@sunzhaoyang 您好，我已经根据您的feedback做了相应的修改，麻烦您帮我看看还有没有什么需要改进的地方。多谢！

[sunzhaoyang]

LGTM 不过我建议 TOC 先不加，等重构的 PR 合并之后我再做一些合并的处理 cc @ran-huang

/cc @gozssky

[sunzhaoyang]

LGTM

[sunzhaoyang]

@nova-xu please fix the error of " jenkins-docs-cn/verify "

@ran-huang we have to merge this article with current duplicate detection document

[ran-huang]

@ran-huang we have to merge this article with current duplicate detection document

@sunzhaoyang You mean merge with this doc?

[nova-xu]

@sunzhaoyang I fixed the previous manual line break error, but Jenkins still failed for another reason. I read the detailed information, but I'm not sure if this means my doc didn't pass the markdownlint check.

[ran-huang]

/rebase

[ran-huang]

@nova-xu Hi, sorry for the delayed response. Could you please merge commits from the master branch so we can proceed with the review?

[ran-huang]

/rebase

[ran-huang]

Merged the content in this doc into tidb-lightning-logical-import-mode-usage.md and tidb-lightning-physical-import-mode-usage.md.