feat: tree-select support showArrow

[zkwolf]

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3. Related issue link.
   The suffix icon is not displayed when TreeSelect multiple selection #4350

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[tangjinzhou]

单测没跑过

[tangjinzhou]

showArrow 应该是判断了 undefined 之类的

[zkwolf]

囧，我晚上再看看

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.