Toggle draft merge requests in homepage

Problem to Solve

As part of the work for the homepage, there are some use cases where seeing DRAFT merge requests may not be beneficial or actionable for users. There's currently no way to exclude these merge requests from the view or count so they can create noise.

Proposal

1. Under the display preferences we should add an additional option for:
   • Show drafts <toggle>
   • This would be default to true (toggled on), but could be toggled on/off for users and their preference would be saved each time they visit the page.
2. Only drafts in "Your merge requests" would be hidden
   • Discussion #551475 (comment 2689308921)
3. When drafts are hidden, the number of drafts is excluded from the active count.
4. When drafts are hidden and the number of drafts hidden are displayed in the footer
   • Label would read # drafts hidden
5. When drafts are hidden and the number of drafts is zero, don't display the footer.

Mockup