Accessibility update for tooltip.js

Accessibility update for tooltip.js

Update to the tooltip.js to add an aria-label attribute that contains the original title of the element, but only if the element doesn't have an existing aria-label attribute.

This is to address cases where screen readers are not capturing the aria-describedby attribute that is added when the tooltip is triggered.  This should also avoid a race condition between the screen reader and the appearance of the tooltip.