In this pull request I've changed a ton of method signatures to reflect the more-narrow types of Species, Move# and Form; additionally, I've narrowed other large collections that stored lists of species / permitted values, and reworked them to be more performant with the latest API spaghetti that PKHeX provides. Roamer met locations, usually in a range of [max-min]<64, can be quickly checked using a bitflag operation on a UInt64. Other collections (like "Is this from Colosseum or XD") were eliminated -- shadow state is not transferred COLO<->XD, so having a Shadow ID or matching the met location from a gift/wild encounter is a sufficient check for "originated in XD".
`Moveset` struct stores 4 moves, and exposes methods to interact with a moveset.
`IndividualValueSet` stores a 6 IV template (signed).
Performance impact:
* Less allocating on the heap: Moves - (8 bytes member ptr, 20 bytes heap->8 bytes member)
* Less allocating on the heap: IVs - (8 bytes member ptr, 28 bytes heap->8 bytes member)
* No heap pointers, no need to jump to grab data.
* Easy to inline logic for checking if moves are present (no linq usage with temporary collections).
End result is faster ctor times, less memory used, faster program.
Rewrites a good amount of legality APIs pertaining to:
* Legal moves that can be learned
* Evolution chains & cross-generation paths
* Memory validation with forgotten moves
In generation 8, there are 3 separate contexts an entity can exist in: SW/SH, BD/SP, and LA. Not every entity can cross between them, and not every entity from generation 7 can exist in generation 8 (Gogoat, etc). By creating class models representing the restrictions to cross each boundary, we are able to better track and validate data.
The old implementation of validating moves was greedy: it would iterate for all generations and evolutions, and build a full list of every move that can be learned, storing it on the heap. Now, we check one game group at a time to see if the entity can learn a move that hasn't yet been validated. End result is an algorithm that requires 0 allocation, and a smaller/quicker search space.
The old implementation of storing move parses was inefficient; for each move that was parsed, a new object is created and adjusted depending on the parse. Now, move parse results are `struct` and store the move parse contiguously in memory. End result is faster parsing and 0 memory allocation.
* `PersonalTable` objects have been improved with new API methods to check if a species+form can exist in the game.
* `IEncounterTemplate` objects have been improved to indicate the `EntityContext` they originate in (similar to `Generation`).
* Some APIs have been extended to accept `Span<T>` instead of Array/IEnumerable
