uni-data-picker为何不考虑增加动画效果

**新功能描述**
uni-data-picker为何不考虑增加动画效果
直接弹出显得太僵硬了

**现状及问题**
uni-data-picker为何不考虑增加动画效果
直接弹出显得太僵硬了

Start at the uni-data-picker component entry point and inspect how it currently appears when opened. The issue does not specify the animation style, timing, supported behavior, or tests, so clarify those expectations with maintainers before implementation. Done means the picker opens with the agreed animation rather than appearing abruptly.

Written by the indexing model from the issue text.