We implement simple state machine iterators to iterate through every split type encounter array, and more finely control the path we iterate through. And, by using generics, we can have the compiler generate optimized code to avoid virtual calls.
In addition to this, we shift away from the big-5 encounter types and not inherit from an abstract class. This allows for creating a PK* of a specific type and directly writing properties (no virtual calls). Plus we can now fine-tune each encounter type to call specific code, and not have to worry about future game encounter types bothering the generation routines.
* Extract/encapsulate inventory legal arrays to interface+class
Hiding them behind methods allows these to be left as ReadOnlySpan<ushort> and thus never allocate on the heap.
Also refactors out some logic for checking if an item is legal.
End result feels more maintainable and is less bloaty (no more passing in a nullable func)
Batch editing
* Add HasType filter
```
=HasType=11
.HeldItem=Meadow Plate
```
slaps a meadow plate on any pkm with grass type
Use `=PersonalType1=11` for only primary grass types; only-secondary-type grass will not match it.
