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/scripts/Spells/spell_druid.cpp

@@ -250,7 +250,7 @@ class spell_dru_t10_restoration_4p_bonus : public SpellScriptLoader
                         return;
                     }
 
-                    Unit* target = SelectRandomContainerElement(tempTargets);
+                    Unit* target = Trinity::Containers::SelectRandomContainerElement(tempTargets);
                     unitList.clear();
                     unitList.push_back(target);
                 }