[Datepicker] Need affordance for open-on-click for inputs

#### Bug, feature request, or proposal:
feature

#### What is the expected behavior?
When i click on input - i want to see calendar without click on icon and input must be focused

#### What is the current behavior?
To view calndar i need click on icon... and input not focused

#### What are the steps to reproduce?
Use datepicker and click on input (not icon) - calendar not opened... when click on icon - calendar opened, but input not focus

首先复现所描述的 datepicker 行为：点击 input 而不是 icon，并观察日历是否打开以及 input 是否获得焦点。阅读 datepicker 组件的入口点及其现有测试（如果有），然后验证这两种交互是否都产生预期的打开和焦点行为。

由索引模型根据 Issue 内容生成。