Instead of allocating a buffer for Storage/General, just point within the raw Data, as a Memory<byte> reference. Most of the uses were already using it as span.
Increase abstraction for arbitrary slot get/set operations, and fracture
SAV4 behavior for each game type.
Adds: Undo/Redo of party slot changes
Fixes: Fixed Gen5 daycare slot 2 reading, and EXP reading
Fixes: Some slot color glitchiness
Fixed: Box layout editor now hides the flag label if no flags are
present
Fixed: Gen7 box flags are now shown (unknown purpose lol)
Changed: savefile objects are generally smaller (removed a few shared
offset fields)
