1. Do not modify the map after loading. Instead, return string views
(guaranteed to be null-terminated) from look up functions and return
the key directly if not found.
2. Use an `unorded_map` instead of `map` where available (C++20).
Saves a bit of RAM (~50 KiB) and improves lookup performance.
Previously this was falling back to FunctionCase, leading to inconsistent casing of class methods throughout the codebase. Applied to Item as an example.
* Move declaration of dItems to items.cpp
This array is never used in dungeon generation, it's closely related to Items so should be kept together. Ideally managing dItems can become responsibility of a container for Items, which will handle adding/removing items from the list and keeping the positions in sync.
* Rename SetPlrHandItem to match purpose/use
* Give more descriptive name to GetPlrHandSeed
This function sets a new seed on a given item struct, not just the held item.
* Don't use HoldItem as a temporary for the players initial inventory
* Take Item by reference in RespawnItem
* Don't use holdItem as a temporary when dropping gold on death
* Update DeadItem to take item by reference, and refer to it consistently
Move code which invalidates the source of dropped items to the caller
Most call sites use a temporary item instance or remove the item from the container, so there's no real point invalidating the item after it's been copied to the drop list.
Update DeadItem to take position instead of player references
This allows the calling code in DeltaLoadLevel to behave the same as every other use of DeleteItem, making it possible to remove the duplicate argument and ensure that the ActiveItems/AvailableItems arrays are treated appropriately.