[FIX] web: render all day events (calendar)

The calendar renderer used event.record.allday and not event.allDay
and as such doesn't use the attribute set on the view.
If the model doesn't have a field called 'allday' this can't work.
This commit fixes that.
OPW-2968130

closes odoo/odoo#110669

Signed-off-by: Michaël Mattiello <mcm@odoo.com>
Co-authored-by: Justine Doutreloux <justine.doutreloux@acsone.eu>