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.
EncounterArea now stores a more specific type'd array for encounter slots. Better iteration and less casting, as the nonspecific `Slots` fetch is rarely referenced.
EncounterType renamed to GroundTile to reflect how it actually works in Gen4. Was previously an ambiguous field that was clarified a little; we can describe it a little better now. Keep the GUI the same to not scare the end users.
Change Trash Byte properties to get/set a Span. Trash Byte legality checking easier on the garbage collector?
