[Feature Request] Add support for inline datepicker

### Existing Component
Yes

### Component Name
El-Date-Picker

### Description
It would be great to add the option to embed the date-pickers rather than having an input wrapped with a popper.
It's the duplicate of https://github.com/ElemeFE/element/issues/6805 but it's closed a long time ago. It looks like there is also an ongoing re-write of date picker components so it would be great if we can add this functionality as well. (https://github.com/ElemeFE/element/issues/9878)
Looking at the forks, it seems that @kpabi already implemented this feature. See: https://github.com/kpabi/element/commit/317c7104ab0ed88bf146af69b8c4981fbbf369a0, care to create a PR?