dateMenu: Use intervals with non-inclusive ends for date ranges

dateMenu: Use intervals with non-inclusive ends for date ranges

The ical events, we are comparing these intervals to use the first point
in time after the end of the event as their end time, while the code in
gnome-shell was using the last point in time within the range. This was
causing multi-day events ranging from 0:00 to 0:00 to have a trailing
"..." shown on the last day.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2023>