Add support for showing other assignee on project board.
Project task cards now query the other assignee field and adds the user handle to the card. Also modified PHUIObjectItemView so that the handle icons also contribute to the phui-oi-with-n-actions so that the handle icons don't overlap with the card content.
I've used the field key std:maniphest:wm.otherassignee
for testing, but I don't actually know what the field key is on the Phabricator deployment, so it needs be changed to the correct field key before merging.
Bug: T329974