Config: Make Load() and Save() slightly faster

Only invoke config changed callbacks from Config::Save, not
Layer::Save. The latter results in callbacks being called
once per layer, up to 7 times per save.

Source/Core/Common/Config/Config.cpp

@@ -62,12 +62,14 @@ void Load()
 {
   for (auto& layer : s_layers)
     layer.second->Load();
+  InvokeConfigChangedCallbacks();
 }
 
 void Save()
 {
   for (auto& layer : s_layers)
     layer.second->Save();
+  InvokeConfigChangedCallbacks();
 }
 
 void Init()

Source/Core/Common/Config/Layer.cpp

@@ -115,7 +115,6 @@ void Layer::Load()
   if (m_loader)
     m_loader->Load(this);
   m_is_dirty = false;
-  InvokeConfigChangedCallbacks();
 }
 
 void Layer::Save()
@@ -125,7 +124,6 @@ void Layer::Save()
 
   m_loader->Save(this);
   m_is_dirty = false;
-  InvokeConfigChangedCallbacks();
 }
 
 LayerType Layer::GetLayer() const