feat(pro:search): support searchField placeholder

[sallerli1]

PR Checklist

Please check if your PR fulfills the following requirements:

• 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?

搜索输入不支持placeholder

What is the new behavior?

新增搜索输入placeholder属性配置

Other information

[idux-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #1322 (6eac01f) into main (7620e5d) will increase coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 6eac01f differs from pull request most recent head 0c395b7. Consider uploading reports for the commit 0c395b7 to get more accurate results

@@           Coverage Diff           @@
##             main    #1322   +/-   ##
=======================================
  Coverage   93.13%   93.13%           
=======================================
  Files         324      324           
  Lines       29980    29982    +2     
  Branches     3399     3399           
=======================================
+ Hits        27923    27925    +2     
  Misses       2057     2057           

Impacted Files	Coverage Δ
...ckages/components/_private/overlay/src/Overlay.tsx	95.54% <0.00%> (+0.01%)	⬆️
packages/pro/tree/src/ProTree.tsx	96.31% <0.00%> (+0.01%)	⬆️

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