Find a way to show full group names when truncated in touch devices

With https://github.com/hypothesis/client/pull/7289, we addressed a layout issue for too long group names, by truncating them when there's not enough space.

The full group name can still be seen on hover, but touch devices don't have a way to trigger that, so we need to find a way to display the full group name somehow.

One suggested option would be to show it on long press, but touch devices usually use this to select text and present some floating controls to copy it and related actions, so it's not great.