search: Only highlight current filter when input has focus
Created by: fkling
I think it's a better experience if the token is not highlighted if the input doesn't have input.
https://user-images.githubusercontent.com/179026/161580355-e2a5e31f-ec7b-41c4-a948-b4567b28e5fc.mp4
Test plan
Manual test: Enter multiple filters into the search input. Moving the cursor (via keyboard or mouse) should update the filter highlight. Removing focus should remove the highlight. Refocusing the element should highlight the filter again (if any).