Copied from T246294.
Pin buttons should only be visible for the cell being hovered on, and should disappear again on mouseout (including when a highlight is pinned) - MEDIUM
- When hovering over a row, the pin button should show up only on that row (and not on all the matching/highlighted ones).
- Once an item is pinned, the pin button should not be visible if the highlighted row is not being hovered on.