chore(hoverPlaceholder): optmize logic when value is not empty

[kerm1it]

#25050

@afc163 看看是不是这种效果？

@zombieJ 优化了有值是的情况，悬停时输入框的值变为对应日期，样式变为 placeholder的样式，离开后恢复原值。

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[codecov]

Codecov Report

Merging #109 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #109   +/-   ##
=======================================
  Coverage   99.58%   99.58%           
=======================================
  Files          44       44           
  Lines        1920     1924    +4     
  Branches      575      584    +9     
=======================================
+ Hits         1912     1916    +4     
  Misses          6        6           
  Partials        2        2           

Impacted Files	Coverage Δ
src/Picker.tsx	100.00% <100.00%> (ø)
src/RangePicker.tsx	100.00% <100.00%> (ø)
src/hooks/useHoverValue.ts	100.00% <100.00%> (ø)

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[kerm1it]

重构了一下，其实已经和 placeholder 没有关系了，hover 时的样式那的类名还是叫 placeholder。

[zombieJ]

+ rc-picker@1.15.0

[afc163]

在 Firefox 下选择时，第一个和第二个日期都会有灰色和黑色的短暂跳动。

Chrome 下很流畅，看不出来。

[kerm1it]

需要给事件加个防抖