Autosave `due_date` in Issuable form

What does this MR do and why?

• Autosave due_date in Issuable form

Screenshots or screen recordings

How to set up and validate locally

1. Open a new issue : http://127.0.0.1:3000/flightjs/Flight/-/issues/new
2. Select a 'Due date'
3. change type to 'Incident'

Due date is persistent

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 #357045 (closed)