Create string overflow utility

[davidmenendez]

we now have a utility to handle truncating / overflowing arrays of items with useOverflowItems for components like TagOverflow and ActionBar. The next piece we need is to implement a utility that can consolidate the same functionality in StringFormatter and DelimitedList.

The overflow functionality in these two components is essentially just converting the element into a popover if the width exceeds the container. PageHeader has very similar logic using the checkHeightOverflow utility. All of these pieces should be able to utilize the same overflow behavior to deal with truncating a single long string.