fix(pro:search): treeSelect panel height is unset

[sallerli1]

add height prop and fix it to 256 so that treeSelect panel wont be too high

PR Checklist

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• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

What is the current behavior?

treeSelect 类型面板没有设置高度，会导致超长

What is the new behavior?

暂时固定高度为 256px，和目前的 select 面板一致，后续考虑是否要增加可配置

Other information

[idux-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #1445 (f709e89) into main (8852db4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1445   +/-   ##
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  Coverage   92.98%   92.98%           
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  Files         327      327           
  Lines       30350    30350           
  Branches     2559     2560    +1     
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  Hits        28221    28221           
  Misses       2129     2129           

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