feat(pagination): Show ellipsis when rotating

When we have more pages than can be shown and we're rotating, shows ellipsis' like:

Previous, ..., 3, 4, 5, 6, 7, ..., Next

This also adds a handy function in the tests to convert the pager to a string, so that we can intuitively check the state of the pager all at once, instead of having to check each element's text individually.