Rebuild active_item cache for vehicles after refresh

[robob27]

Summary

Bugfixes "Some items taken out of fridges rot immediately"

Purpose of change

Fixes #58824

Describe the solution

After we modified vehicle::refresh() to add/remove fake parts, it seems to have started causing issues with the active_item cache for vehicles. More information in my comment here. TL;DR, vehicle::refresh caused active_items to become empty, which caused items inside the vehicle not to be processed for rot etc.

It seems we need to refresh the active_item cache as part of vehicle::refresh now based on this. So I made the following changes:

• Add a new method vehicle::refresh_active_item_cache to encapsulate the logic for setting up active_items
• Call the new vehicle::refresh_active_item_cache method at the end of the vehicle::refresh method
• Stop setting up active_item cache directly in vehicle::deserialize - this method calls vehicle::refresh which handles this now by calling vehicle::refresh_active_item_cache.

Describe alternatives you've considered

• Maybe adding fake parts to vehicles isn't supposed to impact active_item cache and this isn't the right solution. At the very least I hope my naive attempt at fixing this might serve to push someone with a bit more context towards the right solution.

Testing

Using the debug stuff described here I verified that after applying the changes, items in fridges were no longer frozen in time after a save/load, and had rot values updated as expected while waiting nearby.