Migrate epic sidebar datepickers to date widget

What does this MR do and why?

Migrates epic sidebar date pickers to date widget so that it's consistent with epic boards.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #332303 (closed)