Dropdown elements should have associated labels per https://www.w3.org/WAI/tutorials/forms/labels/
Setting the JS tooltips for the "Manage" and "Fullscreen" dropdowns also as their `aria-label` is clearly more accessible than exposing no hints at all.
Regarding the implemention,
* `$action->getName()` would return null as no name is set to be rendered in the UI next to the icon.
* introducing `$action->getTooltip()` in `PHUIListItemView` would also return null as this tooltip is created via JavaScript in `PhabricatorProjectBoardViewController` via `PHUIListItemView()->setMetadata()`. Thus do the ugly dance by parsing that very metadata for the sake of more accessibility on project workboards.
See T16072