Show Draft status instead of Open when MR is Draft

What does this MR do and why?

• Adds a show_merge_request_status_draft feature flag
• Shows Draft badge when MR is Open and Draft to make drafts more distinguishable

Next steps

1. Make badges refreshable
2. Add badges to the activity

References

Feature issue: #419516

This issue was raised here: https://gitlab.com/gitlab-org/foundations/ux-paper-cuts/team-tasks/-/issues/43#note_2476579586

FF issue: #550387

UX Paper Cuts planning issue: #513103 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. In rails console or on http://gdk.test:3000/rails/features/ enable the feature flag show_merge_request_status_draft

   Feature.enable(:show_merge_request_status_draft)

2. Go to any open MR that you have
3. Make it draft via the quick command or a top right kebab button
4. Reload the page. You should see that badge was changed
5. Assign this issue to yourself
6. Go to a list of MRs
7. Find this MR, it should have a new badge

MR acceptance checklist

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