UX: Display full-page user search in a grid (PR #14636)

Before/After

Two reasons for this change:

  1. Better utilization of the screen space (i.e. displaying more than 5 entries on a 13" display)
  2. Making user link elements smaller fixes user-card positioning (it no longer displays far to the right, away from the user name/avatar)

GitHub

Does this cause a bit too much vertical spacing on mobile?

Mobile has 1em