Core/Items: Item bonus generation improvements

* Pass ItemContext to item creation wherever possible
* Support scaling item levels with m+ keystone levels (not used currently)
* Fixed item link validation when client sends it as default uninitialized bonus list with context only
* Support scaling items depending on current active season (seasons not implemented)
* Implemented content tuning redirection
Port From (https://github.com/TrinityCore/TrinityCore/commit/0fb8765a6638fd947b59fce44d5c31251d0cdadd)

Source/Game/Spells/SpellInfo.cs

@@ -4306,7 +4306,7 @@ namespace Game.Spells
                         expansion = contentTuning.ExpansionID;
 
                     uint level = caster != null && caster.IsUnit() ? caster.ToUnit().GetLevel() : 1;
-                    tempValue = Global.DB2Mgr.EvaluateExpectedStat(stat, level, expansion, 0, Class.None) * BasePoints / 100.0f;
+                    tempValue = Global.DB2Mgr.EvaluateExpectedStat(stat, level, expansion, 0, Class.None, 0) * BasePoints / 100.0f;
                 }
 
                 return (int)Math.Round(tempValue);