View shared resource bookings in Resource planner

BRP-8792

Purpose

When clicking a workshift in Resource Planner, a "Shared resource bookings" dialog now shows persons booked on that resource. A new system setting showEntriesOnOtherResourcesWithSameProductLabel (default: off) can be enabled to also show persons booked on other resources with the same product label on the same workshift (intended for entrance bookings with resource requirements).