Core/Shared: Move container functions to shared project under Trinity::Container namespace. Also implement RandomResizeList which takes a predicate function as parameter.

Core/ScriptedAI: Extend SummonList::DoAction to take a predicate function as parameter and allow specifying a maximum number of units to be selected.

src/server/game/Entities/Unit/Unit.cpp

@@ -14956,7 +14956,7 @@ Unit* Unit::SelectNearbyTarget(Unit* exclude, float dist) const
         return NULL;
 
     // select random
-    return SelectRandomContainerElement(targets);
+    return Trinity::Containers::SelectRandomContainerElement(targets);
 }
 
 void Unit::ApplyAttackTimePercentMod(WeaponAttackType att, float val, bool apply)