Core/Game: Rewrote the ScriptMgr to support script reloading.

* Finally this commit enables dynamic script hotswapping
  and finished the PR #15671.
* Split the storage layout to use optimized storages
  for database bound and unbound scripts.
* Add several unload workers to reload scripts correctly
  -> Requires further investigation.
* Fixes memory leaks in ScriptMgr when dropping invalid scripts.
* Fixes VehicleScripts
* Makes OutdoorPvP scripts reloadable
* Makes InstanceMapScripts reloadable
* Makes CommandScripts reloadable

src/server/game/Entities/GameObject/GameObject.cpp

@@ -73,9 +73,15 @@ GameObject::~GameObject()
     //    CleanupsBeforeDelete();
 }
 
-bool GameObject::AIM_Initialize()
+void GameObject::AIM_Destroy()
 {
     delete m_AI;
+    m_AI = nullptr;
+}
+
+bool GameObject::AIM_Initialize()
+{
+    AIM_Destroy();
 
     m_AI = FactorySelector::SelectGameObjectAI(this);