Bug 31261: Disable dates in the past for curbside pickups

Bug 31261: Disable dates in the past for curbside pickups

When creating a new pickup the dates in the past won't display any
available slots. It would be better to disable them in the date picker.

Test plan:
Setup curbside pickups for your library (see bug 30650 test plan if
needed)
Create a new pickup (staff and OPAC) and confirm that the date picker widget
has the dates in the past disabled.

QA note: More work would be needed to sync calendar.inc code between
OPAC and staff. Also note that the "clear date" code wasn't needed
(please confirm).

Sponsored-by: Association KohaLa - https://koha-fr.org/
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>