fix(pro:search): zIndex should be updated only when focused change

[sallerli1]

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?

proSearch的z-index计算不正确，应当只在focused（即激活）时更新zIndex

What is the new behavior?

渲染时就默认更新了zIndex，引发了渲染在弹窗开启之后而导致的zIndex异常

Other information

[idux-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #1356 (5b4bdcd) into main (84d0e66) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #1356   +/-   ##
=======================================
  Coverage   93.09%   93.09%           
=======================================
  Files         323      323           
  Lines       29896    29895    -1     
  Branches     2465     2465           
=======================================
  Hits        27832    27832           
+ Misses       2064     2063    -1     

Impacted Files	Coverage Δ
packages/pro/search/src/ProSearch.tsx	17.31% <0.00%> (+0.09%)	⬆️

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