Core/Spells: rework part 1: Improved positive detection logic

Port From (https://github.com/TrinityCore/TrinityCore/commit/1e1415a49128d034c8d48aa8cbb5d157200371b0)

Source/Game/Spells/SpellManager.cs

@@ -2615,7 +2615,6 @@ namespace Game.Entities
 
                     foreach (SpellInfo spellInfo in spells)
                     {
-                        // TODO: validate attributes
                         if (attributes.HasAnyFlag((uint)SpellCustomAttributes.ShareDamage))
                         {
                             if (!spellInfo.HasEffect(SpellEffectName.SchoolDamage))
@@ -2763,9 +2762,6 @@ namespace Game.Entities
                                 break;
                             }
                     }
-
-                    if (!spellInfo._IsPositiveEffect(effect.EffectIndex, false))
-                        spellInfo.NegativeEffects[(int)effect.EffectIndex] = true;
                 }
 
                 // spells ignoring hit result should not be binary
@@ -2854,6 +2850,8 @@ namespace Game.Entities
                     spellInfo.AttributesCu |= SpellCustomAttributes.SchoolmaskNormalWithMagic;
                 }
 
+                spellInfo.InitializeSpellPositivity();
+
                 if (talentSpells.Contains(spellInfo.Id))
                     spellInfo.AttributesCu |= SpellCustomAttributes.IsTalent;