Add formcount for scatterbug/spewpa

USUM had 20 for both, but XY/AO/SM had only 1 (vivillon had 20); make
them consistent so that our generated evolution paths behave correctly

Add meowstic specific evolution form modifier... so silly
simpler to have it inlined with the sSpecies, for jit optimization

could probably do this with silvally but meh, things work fine now

Closes #2603

PKHeX.Core/Legality/Evolutions/EvolutionTree.cs

@@ -113,7 +113,7 @@ namespace PKHeX.Core
                         if (dSpecies == 0)
                             continue;
 
-                        var dForm = sForm;
+                        var dForm = sSpecies == (int)Species.Espurr && evo.Method == (int)EvolutionType.LevelUpFormFemale1 ? 1 : sForm;
                         var key = GetLookupKey(dSpecies, dForm);
 
                         var link = new EvolutionLink(sSpecies, sForm, evo);