InputDatetime UTC异常

#### 描述问题：

启用UTC 且配置了format, 在选择器中选择后, 文本框中显示的时utc值, 而且选择器中的选项也乱跳.

在显示及用户选择时,应该还是以用户本地时间为准吧?

版本: 1.9

操作步骤
在官网示例中 可以重现问题: https://aisuda.bce.baidu.com/amis/zh-CN/components/form/input-datetime#utc

Start with the InputDatetime UTC example at https://aisuda.bce.baidu.com/amis/zh-CN/components/form/input-datetime#utc and reproduce the issue with UTC enabled and a format configured. Trace the component's display and picker behavior after selecting a value. Done means the text box and picker continue to use the user's local time without jumping.

Written by the indexing model from the issue text.