Add draft filter to Vue merge request list app

What does this MR do and why?

For #442922 (closed)

Adds the MR draft filter to the Vue MR list search bar.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

-	Before	After
No draft filter
Filter option dropdown
Draft=yes	x
Draft=no	x

How to set up and validate locally

1. Enable the vue_merge_request_list feature flag in the rails console rails c => Feature.enable( :vue_merge_request_list )
2. Have or create an MR that is marked as a draft
   1. It will help to have at least one other MR that is not a draft
3. Navigate to the Merge Request list e.g. http://gdk.test:3000/[YOUR USERNAME]/[THE PROJECT NAMESPACE]/-/merge_requests
4. Begin typing draft in the search bar
5. Select Yes or No
6. Submit the search / filter
   1. Try this with the opposite option that you didn't choose
   2. Try refreshing the page completely to test the URL search parameter on initial load
   3. Try clearing the draft token filter and submitting that to see all the MRs become visible