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?
GetCanKnowMove should be checking for Smeargle knowing thousand arrows/waves.
GetNeededMoves should also return 1ka/1kw for needed moves, and then no encounters.
All uses of InvalidSketch are behind that method, so any future Smeargle modifications (like sketching a dummied move) will be checked (yay BDSP considerations).
