fix(picker&date-picker): handling when rolling too fast & remove redu…

[xxyan0205]

背景描述

1. 当快速滚动多个列时，因前一列滚动还未结束，回导致当前列滚动无法正确拿到滚动位置，从而导致无法确定activeItemIndex。[bug-report] Picker && DatePicker 多个column同时快速滑动，停留值异常 #632
2. picker-column和picker-column-list上都存在padding 0 40px，导致内容区域拥挤

主要改动

1. 兜底处理，重新定位到起始位置
2. 去掉picker-column-list上padding

需要注意

[codecov-io]

Codecov Report

Merging #633 into dev will increase coverage by 0.07%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             dev     #633      +/-   ##
=========================================
+ Coverage   83.4%   83.48%   +0.07%     
=========================================
  Files         98       98              
  Lines       2772     2773       +1     
  Branches     527      528       +1     
=========================================
+ Hits        2312     2315       +3     
+ Misses       315      314       -1     
+ Partials     145      144       -1

Impacted Files	Coverage Δ
components/picker/picker-column.vue	84.37% <0%> (+0.09%)	⬆️
components/date-picker/index.vue	93.9% <0%> (+1.01%)	⬆️

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