feat: alwaysClearable prop

[Georglider]

Describe your changes

I have added a prop which makes the clear-icon slot present regardless of the state of the DatepickerInput
It might help developers who have created their own logic for the clear button

Checklist before requesting a review

• I have performed a self-review of my code
• I have ensured that unit tests pass without errors
• If it is a new feature, I have added a new unit test -> There isn't any test for clearable prop