permit necrozma formes 1&2

and 0.
was eventually reaching the Battle Megas list so insert this abort-early
detection.

PKHeX.Core/Legality/Checks.cs

@@ -2007,6 +2007,7 @@ private void VerifyForm()
                 case 800 when pkm.AltForm == 3: // Ultra Necrozma
                     AddLine(Severity.Invalid, V310, CheckIdentifier.Form);
                     return;
+                case 800 when pkm.AltForm < 3: // Necrozma Fused forms & default
                 case 778 when pkm.AltForm == 2: // Totem disguise Mimikyu
                     AddLine(Severity.Valid, V315, CheckIdentifier.Form);
                     return;